Bluray? Definitely. Yes, it's a slower drive. But it gives developers a lot more freedom when it comes to content.
Take Forza 3 for example. They couldn't fit the whole game on a single disc, and the second disc needs to be installed. Those without harddrives are screwed. Whereas GT5 should be on 1 bluray disc, and has twice as many cars as Forza 3, and probably a similar number of tracks.
Then there's id tech 5. id's megatexture technology would benefit from Bluray. Rage on the XBox360 is supposed to be 2 or 3 discs. Now, id has said that the game isn't broken up due to not being able to fit the entire game on an XBox360 disc, and I believe them. But imagine if some other developer using the id tech 5 engine DIDN'T want to break up their game. Imagine if they wanted to create a huge, free-roam, seamless world that couldn't fit onto an XBox360 disc. Bluray would let them create that world.
Then there are JRPG's. Star Ocean 4 supposedly has a lot of disc swapping if you want to go to previous worlds. FF13 is going to feature less video/no audio compression on the PS3 (minor difference that don't affect gameplay, but a difference nonetheless).
As for the Cell, I'm more torn about that. I don't think that the cell is the "best" for gaming. It has it's strengths and it's weaknesses. Whether or not it's better than the XBox360 CPU will depend on what you want out of your processor. That said, it has created 2 of the best looking games so far, in Uncharted 2 and Killzone 2. So while I won't say it's better or the best, I will say that it's done it's job.