I watched TNG from beginning to end and throughout it tried to see anything to be critical of about Wesley and couldn't find anything. What's the big deal?
Well, at the time the main complaint people had was more about him being shoehorned into things in a way that didn't make sense combined with him being "superkid".
But yeah, I always thought the character was more of a positive than a negative, even when he was badly written. If nothing else, it gave younger viewers/fans a bit of a viewpoint character that was pretty rare in sci-fi that wasn't kid oriented to begin with.
Plus, Wheaton did damn fine job considering the scripts were sometimes not really good dialogue for him. Stilted, a bit too "I'm an adult trying to write a teenager, but can't actually remember what it was like"; and often not really about his character as much as they needed someone to do the things he was doing, and Wesley's turn came up. Hell, if you factor in the shit the guy was going through at home, he was amazing.