I think somebody on the BioWare forums said that all Infinity Engine games work on Windows 7. Probably because they don't demand many (if any) processor-specific functions.
Personally, I don't see why you'd be turned off by the graphics in BG. They're still among the best 2D graphics in gaming. As for how BG2 compares, I think that depends on what you're looking for. BG2 is much longer, a little less linear, and more open-ended (although it does discard things like "forest treks to get to your destination"). If you're a fan of Infinity Engine games, I recommend Icewind Dale. It's more shallow and linear than the BG games, but it's also more straightforward and less confusing. A great game if you're looking for a good CRPG to play during a long school semester.