So, most of my friends own a copy (or every copy) of Munchkin, so I decided that buying one was a little silly (at least two of them keep their copies in their cars, and these are the ones I always game with), so I bought Monty Python Fluxx. What I didn't realize at the time was how often we'd want to play it.
It's not that unusual for us to randomly game when we are together, so at least once a week we end up playing something. When we play Munchkin (sorry I'm using the M-word so much. :p), it's a planned event, but Fluxx is a little different. All I have to do is appear and before they've even said hi to me, somebody's asking "Do you have Fluxx??"
The day I bought it, we ended up playing several different games at the comic book shop (Munchkin, Citadels, and Fluxx), with me running an on the spot demo with almost no experience with the game prior to that. In just a couple months, we've probably played 50 games of Fluxx. I'm looking forward to getting other decks, but we're quite okay with the one we have now. And it's totally common to see a group of us in the middle of a cafe with our ridiculously silly accents singing the Lumberjack Song or something from Spamalot.
Fluxx wins for sure.