I own 4 of those games, but unsure why Sonic Adventure 2 would be worth so much. It’s been ported many times, and even as a fan of the series this game doesn’t hold up.
I recently played it on PS3, and it felt so sloppy. I don’t even like 2/3rds of the game, however the Sonic & Shadow stages are alright. Let’s not forget the amazing LIVE & LEARN track!
If you own a Dreamcast buy a GD-EMU clone ODE, you’ll save so much money, no more grinding disc noises, and games load slightly faster.


