Although nothing Ultimate rivals Spidey in terms of consistant quality (apart from the very short Ultimates 1 and 2), I recommend Ultimate X-Men.
It drops off in the latter third of the series (when Robert Kirkman, in a strange exhibition of completely dull writing, takes over), so you deal with it, but before that, it's excellent. Possibly more awesome than Ultimate Spider-Man, but just less consistantly good.
I'm in an Ultimate X-Men mood though.