Not sucked, but perhaps didn't get as much until later.
Dave Ghrol: When Nirvana got big, I didn't get what the big deal was and certainly didn't get why everyone was calling Ghrol such a great drummer. Competent, solid, right for the band, sure, but not great. But over time hearing/seeing what he's done with the Foo's, and various other projects, I get it now. And I even (somewhat reluctantly) admit he's influenced my playing.
Chad Smith. Again, competent, and right for the Peppers. Good player, but not quite the great some make him out to be. I didn't get why he was getting hired for so much session work, and why so many hold him in such high regard. Then I saw him live at one of the Bonham tribute shows. He came out and played Achilles Last Stand, and just rocked it, and played with so much confidence and energy, and yet barely broke a sweat. And I realize, yes, if I were hiring a drummer for a rock session, thats exactly what I'd want.