I'd have to say Halo. Its one game or series of games that I do not like and rag on a lot (although not recently...until now that is

)
In the end though, to each their own. It's just not my cup of tea and I found it lacking. If other people enjoyed their experiences with it, that's fine and dandy for me
[added]
Though I also voice my anger at Black Ops also...even though I play it like a little ***** :/