Speaking as someone who isn't a fan of either series. I got Gears 2 as a present, and have never played it. I can say I think it really renders down to which directer treats their subject matter with real reverence, and not winks and nods to the fans. Comedy is a temptation and it is the quickest path to damnation. These film adaptations need to honor the game as much as possible, but not at the expense of making something that stands on its own two feet.
That said I would go with Gears of War. Underworld may have been deadpanned by many a critic. However what cannot be denied was it actually had a real story arc, and it was treated in a very serious matter. In fact the director has my utmost respect for not falling back on cliches when it came to subject matter. The Vampires weren't blood whore sex objects, and then on the other side the Werewolves weren't vicious animals terrorizing some small group of people.
I think its all about who will treat it serious enough to dare to make a game into a great movie. Rather then make a movie that just panders to those that play the games. For that you need a strong creative center. Who is not going to get cornered in by conventions. Guess which one of those directors that applies to.









