I had to go with the C64. It wasn't just a games console, though, and I certainly used it for a lot more than just games, but that seems an aside.
The PSX (and DC, et al.) had more advanced games, but was a far cry from the C64 in technology too. There's only one way to even compare them, and that's on the gaming experience itself: how much fun did I have playing games for each system, and for how long. I loved games on the 64 and for far more years than I even owned a PSX.