I find it interesting that it has been over 10 months since my original post, and I still am hard-pressed to name a PS3-only game that is a must-have - for me anyway.
Well, maybe now that HD-DVD is essentially dead, I might get a PS3 as a Blu-ray player that can play games too....
Of course, if Microsoft wants to continue its need-to-take-over-the-world campaign, then they will probably soon announce that they will have a Blu-ray add-on player a la their HD-DVD add-on (which, incidentally, I have seen now in stores for $50!).