My fav system of all time would have to be the PS2. Come on, the PS2 had some of the best games of last gen (doesn't matter if most of them best games were 3rd party, they were still on the PS2), some of the best games of all time.
And as for my current gen systems... I'd have to say the 360. As much as I like Nintendo, and as much as I want to like the Wii (I'm still wanting on SSBB, I haven't beaten LoZ:TP, and I touched SMG the first day and I think the day after and that was it), the 360 is the system I'm on right now. With the shooters I got, and with XBL Gold... I can't ask for more.