I'm amazed this thread hasn't devolved into grunting and brandishing of war clubs.
In the current generation, there are relatively few exclusive titles. If there are some franchises you like a lot, you should consider buying the console that carries those franchises. On the Playstation, I personally love the God of War series and Ratchet and Clank. On the Xbox (really should say Xbox and PC), you have bioware titles (like Mass Effect) and fun little western type games like Overlord and Gears of War. The Dead Alive series is also Xbox exclusive.
The PS3 is a technically superior system but that doesn't tend to matter. Most of us don't have good enough televisions to take advantage of that superiority. Furthermore, the lion's share of non-exclusive titles are developed on the 360 and ported to the PS3, meaning the graphics are virtually the same. (I can't think of a single non-exclusive title that wasn't developed on the 360...though the upcoming FF13 is a PS3 -> 360 port.) You'll get a little more graphical oomph from a vanishingly small handful of PS3 exclusive titles, but I don't think you should make that the basis of purchasing a system.
There are a few less tangible factors to consider when making your choice. The PS3 is still the cheapest Blu-ray DVD player out there. Even if you get a Blu-ray player on some sort of promotion deal (my grandfather recently did) you'll still only save maybe $50 over the cost of a PS3. In many cases, you'll pay an amount equal to the PS3's cost if you buy a dedicated Blu-ray player, even with some sort of promotion deal. If you're a true videophile, the PS3 won't be quite as good as a dedicated player, but chances are you'll never care about that.
A big advantage the 360 has is its ability to stream movies from Netflix onto your TV, which is something I really enjoy. You can stream them onto your PC it's true, and if you have the right PC setup you can stream them to your TV via that avenue, but the 360 is a good plug and play solution.
Both the PS3 and the 360 have their online services and associated communities. Most people consider the functionality and userbase of the 360 to be superior, but take that with a grain of salt. Depending on what games you want to play online, YMMV.
Finally, it's worth pointing out that the 360 has a larger line of varied titles and is so far 'winning' the console war this generation. You can say that the 360 has more shovelware and overall the library of PS3 titles is of higher quality, but if you're fence sitting about buying a console and can't decide, the lineup of games on the 360 combined with the low price makes it a very attractive choice.
(I'll also point out here that if you don't have a PS2 for some reason and want to save money, you can buy a new one for next to nothing and play its huge lineup of games until doomsday.)
