Besides being extremely limited (you can change the resolution, activate anti-alias and v-sync and change shadows from 'low' to 'high' and that's pretty much it), the window is not resizable. The configuration menu itself is horrible as well. For every minor change you have to restart the whole fucking and run the configuration thingy again because the game has the memory of a goldfish. This is bad on itself, but unlike those other games if you plug some headphones, a controller, change the resolution of your PC, update your drivers or anything else the game will refuse to boot up. Speaking of that, like many SEGA games from that era, the configuration menu is separated from the actual game. It either throws me an error, my controller doesn't work, or it tells me my configuration has changed since the last time I played the game. It's short and extremely replayable which would make it the perfect 'I don't know what to play game', but it isn't.

Sonic Generations is always one of the first games I install on any PC.

Sonic generations configuration tool