I have Master System II with Alex Kid (in conosol) and Sonic. The game (sonic) is very good for MS, and the graphic is awesome, for 8 bit console. Variety is not like the Sonic games on Genesis/Mega Drive but is not so bad especialy for the 8 bit system. Pity is that my MS is sunken in dust ???
If you mean Sonic, then I think there are a few minor differences. For example, because of the screen resolution of the GG it is possible to jump up and hit Robotnik as he is flying overhead (first boss). In general, the game is more or less exactly the same.
I think it was not very rare here in Europe, I had the cartridge while some friends of mine had a SMS II with Sonic built-in. IMO it's one of the best Sonic games EVER. Maybe Sonic 2 was the best in SMS, but Sonic 1 is my favourite.
Mmm there are people who don't like Sonic 1 at all... what did you think when you saw Sonic Chaos Masterpiece ?
Choas was a nice game, had some pretty nice effects/graphics. The bonus stages were mostly pretty fun (except that stupid spinning through tunnels one). It suffered from the long standing "another Sonic game that is way too easy" syndrome, that plagued almost the entire series though. A really good showcase of the SMS capabilities.
Yeah, its graphics were good (although they suffered a bit of slowdown in the PAL version), but it was just too easy and you could complete A LOT of stages in a few seconds. In fact, it was one of my Christmas presents and I found it inside my mother's closet two days before :
: and completed it that afternoon, hehe.
Bonus stages were also decent, they were the only difficult task to complete in the game and their variety was interesting. However, SMS/GG Sonic 1 had the best bonus stages, and they were much better than that rotating stage found in Genesis Sonic 1.