The question and the answer imo is JRPG.
If someone is not interested in JRPG's and buys or plans to buy all 360 multi-platformers he/she's interested in for the PC, there are not many reasons left to buy a 360 (you can even skip the few exclusive WRPG's like Fable2 as the PC can easily compete in this genre - and there's a big chance that Fable2 will come to the PC one day).
The PS3 is another story. I still think the library will have more interesting and diverse library of (really) exclusives than the 360 in 1 or 2 years, not only JRPG's. Games like Uncharted, GT, MGS and LBP are just the beginning.
Personally, I quit PC gaming about 10 years ago and up to now I skipped the HD consoles for a simple reason which is rarely mentioned by others (which makes me think I'm the only one with this reasoning):
I don't own a HD TV.
