I do agree that Legolas and Gimli were underserved (particularly as the series went on) but I suppose there was only so much they could do with the film format given how huge the story is. On the other hand, the comedy factor never particularly bothered me. I can see why it might be considered annoying though.

On the other hand, I also see your point about Merry and Pippin. I particularly like the relationship between Merry and Theoden in the novel, but much of that disappears in the film.