I read Deadpool religiously all the way up to and through Agent X. After that I pretty much lost interest, though I do remember picking up a random issue or two of Cable & Deadpool. The only other complete arch I have is the three volume MAX run, which wasn't great, but it wasn't bad either. Part of what made Kelly's run so amazing is that it was the perfect balance of tragedy and comedy. You liked him. You hated him. You felt sorry for him. There was some real depth there. I can't really recall anyone else working with him in such a way.
Yep. It really tugged the heartstrings in a way you'd never have thought possible after how he made a joke of everything at the start. I love me some DP & Cable. He's the straight man with the occasional snarky observation. He's the Ying to Wade's Wang--er, Yang. I highly recommend getting more of the issues. The overarching plots weren't even bad, and that tends to be the weakpoint of even pretty good serial comics.