I'm currently keeping up with all of the Absolute and Ultimate Books.
If I had to pick a Favorite from each, I'd probably go Wonder Woman (With Supes as a close second) for Absolute. I like Batman too, but right now it seems like the safest of the trinity.
GL, MM, and Flash are all still too new to be contenders, but I've really enjoyed Flash and GL.
MM I think I need to give more time to see if it's a good Absolute book, or a good Black Label/Vergtigo book.
For Ultimate, my Favorite is probably X-men, just because Spider-Man would be cheating.
It has beautiful art by Peach, and I love the different view of Mutants in it compared to 616.
Wolverine has some great art, and seeing him struggle against Winter Soldier programing is interesting, but it's still pretty new to judge long term.
Black Panther feels too much like it could also work in continuity aside from Ra and Khonsu being the antagonists.
I like the Ultimates showing off more of the world than the other books, and giving us new heroes each issue, but it feels like the book that reads best in the trade format because of all the jumping around month to month.
If anyone here hasn't tried them, ignore the "hurr everything is terrible all the time from every company" takes, because they ain't reading it anyways.
Try out the trinity for Absolute, and then check out the newer ones if any grab your attention.
Try out Spider-Man, X-Men, and The Ultimates for the Ultimate Universe, and like wise grab any after if they get your attention.
Both universes are very much worth checking out and are enjoyable, and different enough from each other that one of them is sure to grab you.