I highly recommend Elgato HD also. It is $159.99 on newegg right now with $10 rebate. Best features I would say is it will continue recording (up to an hour) even if you don't hit record. So if you forget you are still ok. You can also record your voice with the software at the same time, and even livestream from the software. Cons would be it uses a fair amount of processing power.
The Hauppauge HDPVR2 is okay, it's more basic and I have heard it has software problems, not sure exactly what though. I use to own the first HDPVR and it worked fine, but the only addition to the 2 is an HDMI passthrough and I think slight differences in the software. You can get it for $169.99 at Newegg, $149.99 at Tiger Direct and $135.99 at Amazon.
Again, I recommend the Elgato. It has smaller file sizes and I believe is 1/3 the size physically, also the features are a big pro. Both do record in 1080p though.
And of course as others have said. If you don't want the HD route because you are doing this casually and/or are low on money you can get an easy cap, or preferably the roxio game capture (which can record 720p) for $80, or less than that, a dazzle (which can be bought from Best Buy or Office Depot still) for $40
All up to you. This was longer than I thought it would be. lol