Talledega Nights might be the only movie with him as the lead role that was above moderately good.
Although I will have to admit that I haven’t seen much of his repertoire.
Will Farrell just isn’t a likable sympathetic protagonist, in my opinion.
He was great in Oldschool, but his “Frank the Tank” character was not the main protagonist, and his annoying shouting physical comedy actually worked great in the supporting role. Luke Wilson was the sympathetic character, just like he was in Idiocracy. Luke’s situations are funny because of all the bad stuff that happens to him, but you like him and want him to prevail.
The only other exception I give is Ron Burgundy. But again, as annoying yet funny as his character was, it wasn’t a sympathetic protagonist and his supporting cast made the movies better.
Step Brother was horrible. It had funny parts, but they were terrible people and I didn’t like his nor John C Riley’s characters and was rooting against them the whole time. They never grew on me. No supporting cast to save him. Mary Steenburgen? Womp!
I forgot Anchor Man. Also great.