"For example, Defense of the Ancients vs. League of Legends."
Finally, something worth talking about in this thread.
DotA was a great concept with terrible execution. They did the best they could being a WCIII use-map-settings game, but it really wasn't worth playing.
LoL is an amazingly executed DotA clone. A little too n00b friendly, imho, but still great fun.
If you actually enjoyed all the terrible features in DotA, then HoN is probably for you. Between the terrible graphics and bad UI, you'll feel like you never left 2005.
I don't have much experience with DotA II, but from what I hear, it seems good. Of course, it came out so late that most DotA players have invested so much money into LoL or HoN they can never switch to DotA II.
If you've never played a DotA clone, I'd suggest you give both LoL and DotA II a try and just go with the one you like more.