Tecmo Knight It was just so shocking when it was released because nothing was this violent back then. I remember as a kid, I felt sick when I saw the gruesome killings in this game, but then the desensitization set in and I thought it awesome.
Kung Fu MasterSomeone's gotta show some respect to the originator!
Double DragonI love the ending when you have a 2nd player. After their long journey of teaming up to beat the crap out of thugs, brothers Billy and Jimmy suddenly have to fight each other for Marian's affection.
Final Fight This is basically the game that defines beat em ups for me. It felt like most all beat em ups afterwards were trying to be Final Fight.
Cadillacs & Dinosaurs I added this one mainly because the concept is so weird, but it's a great beat em up too.
and if we were not doing arcade only, I would throw in River City Ransom for the NES.