The thing about fighters that bugs me, more than any other D&D class, is that they suck at defense. They have a billion and one feats designed to hurt people or gain an advantage in combat, but only a handful help prevent the fighter from getting hurt. Fighters, in my mind, should be equally skilled in defense; barbarians are brutes who absorb damage, rangers are designed to work at a distance, and paladins have all sorts of divine advantages. All the fighter has is it skill, and that isn't doing the job in the defense area.
IMHO, fighters would be more interesting if they could successfully fulfill different archtypes; 9 out of 10 fighters are high strength, plate mail wearing brutes. Try designing a lightly armored, dex based fencer without multiclassing or entering a prestige class, and see how he compares to the standard fighter. The class should have been designed with many different styles of combat in mind.
Lastly, I've noticed that fighters seem uninteresting because in most D&D campaigns, they are the most common class. Warriors, men-at-arms, mercenaries, and all the rest run around in armor and try to kill things with swords. Most of them cannot rage, don't have favored enemies or the ability to lay on hands. They are, for all intents and purposes, fighters. Even if they are only using the warrior npc class, there is little to distinguish them from the actual fighters, who are supposed to be elite.
The sad thing is that warrior-types are everywhere, and the fighter, lacking any special abilities, blend in perfectly.