This winter, I picked up a Genesis, an Atari 5200, and an Atari 7800. Here's what I learned:

Sega Genesis: Genesis is a very nice game system, even better than I remembered from '89. The arcade style controllers rock, and there are a lot of really good games for it. Oh, and right now, they're all pretty inexpensive -- and it's not hard to find them CIB. Since the boxes are hard plastic, most of the time they're in good shape. And no console modding is needed - all versions do composite out with just the addition of the proper (proprietary) video cable. So, overall, this is a great system at a great price.

Atari 5200: This system is also very nice, just as I remembered from 1982. With Best Electronics' Gold controllers and a trak-ball, plus a well-chosen selection of games, the console really shines. I stuck to games that either benefit from the analog sticks, work well with the trak-ball, or require two or more buttons. All of them work just great. I have absolutely no complaints about the controllers. To the contrary, for these games they're a very nice upgrade from the Atari 8-bit's one-button controller + keyboard. However, the 5200 is an expensive hobby. One can easily spend hundreds of dollars just getting a decent console, 2 good controllers, a trak-ball, and some games. And then there's the tweaking that's necessary to get the controllers just right. But, in my opinion, it's worth the expense and tinkering. I have an absolutely beautiful 2-port console that works wonderfully and gives me uniquely great gaming fun. (And, yes, as others have said, Adventure II alone makes the system worthwhile; but I'd add that the 5200 version of Star Raiders almost achieves that as well.)

Atari 7800: I had one of these in the early 90s. I bought it at a flea market, and bought some games for it. At the time, I thought it was a system with OK games, good graphics, lousy sound, crappy controllers, and a stupidly tight cartridge port. This time around, I bought some of the 7800 game pads and many games for it, but my opinion hasn't changed. Maybe I'm just not finding the right games, but so far this system seems to lack a reason for being. I already have an extensive collection of Atari 8-bit and VCS games, plus a decent collection of 5200 games. This system's only killer app as far as I can see is that it has a couple of decent coop games (Asteroids and Centipede). Beyond that, it seems like a waste of time and money. But now that I have the system, I'll keep it on hand and see if I come across a good game or two for it.