G.G. Mega Man, Reviewed
My friends over on the Talking Time forums have a tradition they call MEGAMAS, where little metal boys and girls the world over save Christmas by destroying the robot masters of Dr. Wily (or your local/temporal equivalent villian), who has captured ol' Saint Nick. It's a tale as old as time...
Anyhow, someone in the thread linked to all the Roll-chan patches on romhack.ing, and I noticed that the Game Gear Mega Man game had a patch. I found that immediately interesting, given how that in all my decades knowing about the game I've never actually seen anyone talk about it at length.
Thus, I downloaded the patch, loaded it up in my favorite emulator (BizHawk), and entered with no expectations other than that the levels were taken from the NES games and the power-ups bounced when they hit the ground.
The game opens with the ill portent of four unskippable logos:

Sega was the platform holder, so they're to be expected.
Capcom owns the rights to Mega Man, so they're also to be expected.
U.S. Gold was, contrary to what their name would suggest, a British company that spent a decade publishing ports of a whole smorgasbord of games to the smorgasbord of home computers on the market in the UK. (I recall someone mentioning that their name was playing into some latent Ameri-philia that existed in the UK in the 80s and 90s, as if they were providing artisanal imports from the mythical ever-sunny land of California.) A year or two after publishing this game they would be purchased by Eidos Interactive for a boatload of money, which might suggest that they weren't in the best financial shape. (NOTE: I am too lazy to look up earning reports for a company that's been defunct for 29 years.)
Freestyle Software, the actual developers of this game, were also the developers of Mr. Blobby for the Amiga, a couple GG poker games, a couple GG sports trivia games, and not much else. In spite of that less than inspiring track record, I don’t think they were the weak link in this game’s production.
I bring all this up to provide context for the reason I suspect this game is the way it is. Some lesser video game critics have said things such as "The whole package reeks of amateur effort," but I would contend that this game is a classic victim of publisher tomfoolery.
This situation is in contrast to the generally well-regarded Game Boy Mega Mans. Those were also farmed out to third-parties (Minakuchi Engineering for 1/3/4/5 and Thinking Rabbit for 2), but Capcom published them games themselves, meaning they had more direct stake on the quality and budget of the game. Additionally, since Capcom didn't credit those contracted companies, the quality of the games reflected directly on themselves.
The Game Gear Mega Man, being on handheld with a smaller market share and under the auspicies of a lesser publisher, had it harder from the outset.
But enough about the production circumstances for now. Let's talk about the game, starting from the intro:




It's an abbreviated version of Mega Man 4's intro, which is as good of an explanation of the franchise as any.

The fans who made this patch apparently gave this game the subtitle "Mini World." I have no idea if this has any actual basis in shelved release plans for the Japanese market (doubtful), but I think it's cute and fits. Much like the Rockman World series for the Game Boy, this borrows robot masters from the NES titles, but has a decidedly smaller scope.
Now, let's see our roster here:

This isn't the crew from Mega Man 4 or 5 that I would have chosen, but it's good enough, I suppose.
Once you get into the game itself, one thing you'll notice is that the developers pretty much nailed the gamefeel of NES Mega Man (5, specifically). The jumps feel proper. Inching forward works properly. The engine feels stable, capable, and behaves how you would expect. The only suspect things are that you can't jump out of a slide (oof), and you're limited to two shots onscreen instead of three (weird, but okay).
This may not seem like a big deal, but if there's one takeaway I want you to live this review with, it's this: The fact that a no-name British studio was able to nail the feel of the game better than the developers of Rockman World 2 or the WonderSwan Rockman & Forte is a singularly impressive achievement. After all, game developers from the Amiga-zone have gained a reputation over the years of being incompetent creators of platformer games, filling their games with ropey controls, aimless levels, no invulnerability frames, and other sorts of problems. This game manages to avoid all of those sins.
Unfortunately, the game's biggest sin also becomes readily apparent once you start playing it, and stems directly from its accuracy:

Levels are one-to-one recreations of stages from MM4 and 5, with no effort made to shrink them down to fit the screen. There is a token accommodation to this, with the game panning the camera to a different location relative to our hero for each room, but unfortunately some rooms still require leaps of faith over pits to unknown platforms. You can change how the camera is panned manually, but the input for that is apparently... *checks notes* ...holding the jump button down for like 3 seconds and then moving it with the d-pad (I did not know this until after I finished.)

There is a "GG2SMS hack" that gives the game the SMS's wider viewport in exchange for its lower color depth. Unfortunately, the patch is only at version 0.55 and is still quite rough. There's a lot of garbage offscreen, and the sprites, tilemap updates, and scroll bounds are not fully adjusted the new screen size, so the result is less than desirable if you're looking for going for a casual playthrough (though you glitch-art aficionados in the audience might get a kick out of it).

Now, I don't want to imply that the camera is the only bit of jank in this game. There are plenty of other small issues, but unlike the camera they feel like the result of a looming deadline, rather than bad design decisions. Some enemy behaviors are slightly off. Some enemy hitboxes are too large or too small. The bosses are a bit too aggressive, especially whenever they jump (this makes Toad Man actually intimidating!). You have to input your password every time you game over. It's a bunch of little things, but I can't bring myself to hold them against the game.
Once you get to the castle stages, you can feel the looming production deadline coming in at full force:

With this map you'd expect some stages from Dr. Cossack's fortress, but you'd be wrong:

Have a couple robot master stages, will ya?
Oh, but we're not done. Let's take a look at Dr. Wily's castle:

It's Quick Man's stage, but the Man doesn't even have the decency to show up! (I guess he was offended that they nerfed the quick lasers.)
Once you get to the pre-boss hallway, you just warp to final stage (which is a pre-boss hallway of its own).
As far as Wily Capsule fights are concerned, this one's fine. It's not particularly exciting, but it could be a lot worse:

Once you make Dr. Wily explode, you escape Dr. Cossack's exploding citadel (??), roll the credits, and see the old man begging for mercy (I guess he unexploded somehow):


The End!
Overall, even though this wasn't a particularly great game, I had fun with it. It's hard to recommend because none of the stages are original, but that doesn't stop them from being good stages. If you really want to play though a random slice of Mega Man 4 and 5, I'm sure mankind has cooked up worse ways to do it (can I interest you in a J2ME port?).
Really, the most crucial thing about this game is that it managed to make me feel generous towards it (perhaps I was just in a generous mood).
This game might have made me angry if I had gotten it in my stupid entitled kid phase (not that I ever had a GG growing up), or if I had been an adult who paid full price for it back in the day. But, for me now, I can only feel wistful about the fact that the publisher here could not properly see, harness, nor nurture the immense raw talent they had on hand.
I'm not just spitballing when I say that this game was cut down to size. Recently revealed development materials show that there were pitches for 8 stage and 4 stage versions of this game, and the powers that be (US Gold? Capcom?) looked at the Game Gear market and decided it was only worth paying for the cut down version. They wanted the game, and they only cared about having it cheap and fast.
I can't help but wonder what could have been...
What if Capcom worked with the developer directly? What if the developer had the time to implement 8 stages like they had planned? What if they had the time to shrink the stages down to match the screen size? What if this game had been released in Japan as Rockman World G? What if they got the chance to make another one of these? What if this game got made in 1991, rather than 1995? What if we got a whole parallel series of GG Mega Mans, and there was an arms race between Minakuchi Engineering and Freestyle Software?
What if... what if...

FINAL VERDICT
Mega Man (GG) could have been a Good Game, but alas it's only a Serviceable Game.
May your power-ups bounce forevermore...