Somebody else upthread mentioned the plague of "future people" in X-Men--Cable, Bishop, Rachel Summers, et al. I could never abide any of them, either.

I guess what I couldn't really abide was the eighties-nineties X-plosion and the whole swarm of unlikeable mutant characters that it produced. The X-Men work much better for me with a relatively small cast of characters, on a relatively limited scale...but that's a different discussion, I guess.