The ones that are on the Sonic collections, are the crappy Game Gear versions, not the Sega Master System versions (not sure why they did that). And those games aren't the same as their Genesis counterparts with the same name.
... they are pretty much identical (Game Gear and SMS). Sonic 1 had sprite resizing plus minor changes to some boss battles. Sonic 2, spinball, and Chaos are changed even less so I believe. They just tend to be zoomed in a little bit. But not in any way that detracts. It's not like Mega Man on Game Gear.
The biggest difference I've noticed is that when speed running through Bridge Zone some of my jump points need to be altered by a fraction of a second. And the boss battle is fairly different. Same concept. But redesigned to not fill the whole screen like it did before.
Unless if both the SMS and Game Gear versions are crappy, I don't see how one can be crappy and not the other. And I don't see how both versions can be crappy. And Sonic 1 on Game Gear and SMS is arguably better than Sonic 1 on Genesis. Sonic 2, on the other hand, is all Genesis.