He's smarmy, he's kind of a jerk, and I just find him very unlikable overall.
While I don't necessarily agree, I can see why you'd say that. Luckily for you, Uncharted 3 and 4 center quite a bit around his character flaws and what they do both to him and to the people around him. You might find yourself pleasantly surprised by where the whole thing ends up.
There's one sequence that sort of encapsulates this for me. After stealing a certain artifact, Drake is trying to sneak out of a huge compound while security guards search for him. He is climbing around on a watchtower, and there's a security guard right above him. The only way to get past is to reach up, grab the guard, and toss him off the tower to his death.
For some reason, this really bothered me. Here I am breaking into an auction, stealing an artifact, then tossing random security guards to their death when they look for me. Yet, Drake supposed to be the good guy here? The one everyone is rooting for? The guy who, an hour before, was playing Crash Bandicoot on his couch? I know it's probably a stupid overreaction, but I actually turned the game off and walked away at that point yesterday. I don't enjoy playing the bad guy in games, and some of the shit Drake does in the search for what is ultimately his personal fame and fortune is just kinda...distasteful. It's one thing to gun down Nazi's or cultists hell-bent on destroying the world. I don't have much issue with that. But tossing random people off rooftops so you can steal shit? Not really my thing. Probably much of the same reason I don't enjoy the GTA games, now that I think about it.
In the game's defense, they do come back later in that sequence and vaguely imply that the guards were hired thugs, but the connection is iffy (at best) and comes way too late.