Since the game angle has been covered pretty well, I'll come from the videophile angle
Sony
+ Best video output with pretty much all sound formats supported
+ Still one of the best blu-ray players
+ Flawlessly plays most video formats, upto 24mbps m2ts (h.264) with dolby 5.1
+ Video player is very responsive, love the 1.5x mode with sound
- Movies on video store limited to 720p at half the bit rate of Zune downloads
- Hardly any previews/trailers for movies
- You tube limited to lowest quality (if not pre-downloading through ps3youtube.com trick)
Microsoft
+ Zune video store, highest bit rate on the downloadable market (still only 10mbps)
+ Love the instant streaming trailers
- Limited to 768kbps Dolby Digital or pro logic surround.
- Annoying gamma correction in video signal makes perfect calibration impossible
- Microsoft points
- Need gold subscription to watch Netflix, youtube etc.
- Picture viewer and a lot of video players are not true 1080p
Nintendo
+ Netflix works with no extra cost
- Limited to 480p
- Only analog sound support