My opinion:
Back in the early days, I would have said X360: Lost Odyssey, Mass Effect, Bioshock, etc.
But nowadays, Xbox has got nothing.
Luckily, the PS3 was ready to take over, with games like LittleBigPlanet, Valkyria Chronicles, God of War III, Uncharted, the HD remakes, etc.
However, despite all of this, I still find it somewhat of a betrayal that there is such a lack of JRPGs and platformers on the console.
But these days, with games like Xenoblade Chronicles, The Last Story and Pandora's Tower, I've been spending a surprisingly large amount of time on my Wii.
In conclusion, the best console for gaming is... the PlayStation 2. And no, that's not a typo.