Hmm. LBP is fairly exciting although I don't have the patience to build levels myself. I suppose PSASBR has potential to be good, haven't followed it up but it's a brilliant idea. AC3 I'll play on PC.
AC3 Lib isn't a port, it's a separate game with a different location and characters. I'm getting AC3 on PC as well and see AC3 Lib as a good companion to it. I'm a huge fan of AC though so that factors in as well.