The biggest films of the past few years, Avatar and The Dark Knight, were well over 2 hours long.
Of course, when films are shown with commercials they often get edited down so they'll fit. Remember in 2 hrs of TV they need to show 30 mins of commercials (watch any 2 hr TV movie or show on DVD and it's 90 mins).
However, the director's cut of ST:TMP wasn't really any longer than the original because of editing. They shortened a couple of the more sedate scenes and the new stuff was largely replacement visual effects which didn't change the running time at all. Only a couple of scenes were added. It just seemed to be a better film, though, like the extended version of the Abyss.