Meh... I'm not anti-Munchkin, but my opinion is a bit different.
The first couple of times you play are a lot of fun. But the jokes get old (pretty quickly in fact), there is a lot less skill than luck, and tons of screw-your-neighbour cards usually mean the game takes way too long unless people get tired of blocking others and decide to just crown a winner.
Of course, all of the negatives can be trumped by playing with a group of good friends. In that case "taking too long" usually isn't a problem and there is plenty of room to make up your own jokes.
Have you tried Munchkin Quest? It adds a big board that you can explore, persistent monsters roaming around, and a bunch of other new features. Kind of like "super deluxe Munchkin RPG"... although some would argue that it adds content that doesn't really belong there in the first place.