I just got an Xbox 360, so I've been double dipping on some games I already had like the Dreamcast games.
I decided to double dip on Fright of the Bumblebees. It's actually more fun with an Xbox 360 controller (of course, that's no surprise since it was designed with that controller in mind). It plays better on the Xbox 360 than on my low-end PC too. My PC repeats dialog all over the place, and the XBLA version only had a mild hiccup at the end.
I actually got Wallace & Gromit's Grand Adventures for free in a contest (so I guess it's not really double dipping), so I think I'll pick up the rest even though they're still at the original price on XBLA. It's definitely a lot of fun to play the games on TV sitting on the couch. :)