To me, the fighter's role is to be the best at whatever the basic combat techniques in the rules are. So if your game is about attack, damage, AC, and hit points, the fighter should have the best overall numbers. If your game has combat maneuvers or stunts or the like, he should be the best at those. Other combat classes should have compelling mechanics that add on to the basics (rage, stunning fist), or combine fighter capabilities with other niches (tracking, healing). Other non-fighting classes (rogues and spellcasters) should not be as good at combat, period.
The 3e fighter with bonus feats is conceptually near-perfect in this regard, but unfortunately lacking in execution. For one thing, those basic combat mechanics aren't robust enough. There's no active defense mechanic for the fighter to be the best at, and not enough effects that can be inflicted on an enemy for a fighter to inflict them well, and not enough attacking options for the fighter to be the best at. The other problem is that fighters are the kings of dead levels; their insufficient class abilities and the lack of high-level abilities mean that they are only balanced for a few levels and require a lot of prestige-class-related machinations to be even competent at higher levels. A good retrofit of advanced combat rules and a rewrite of the class with additional class abilities solves these issues pretty well; PF and TB are both along the right lines, but neither goes far enough alone.