it seems like fighters have essentially the same gameplay style from level 1 through level 20, just with more hitpoints and without all the fun stuff that casters get.
Herzog has it right. Wizards get spells, rogues get skills, and fighters get feats. You pick a fighter class if you want to be feat-obsessed.
Sharkon also hit on a good point -- even just a single level of barbarian can do you real good. Make it your first level, and pick human for your race. You'll get two feats, and you can do exactly what Sharkon said and then roll right into fighter.
As for what *I* do to make fighters more interesting, well.... First, I have a house rule for the game I DM. That is: fighter bonus feats are awarded at any level that a normal feat is
not awarded. (Levels 1, 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20). By level 20, this gives 3 more feats than normal. That allows a level 20 fighter to essentially have a whole extra mini feat chain from the house rule. By level 5 or 6, you have one more feat than a "normal" fighter.
Second, although I do not allow Book of 9 Swords into my campaign (a very "martial power on steroids" kind of book), I do allow all the Complete books, along with the PHB 2. So I try to take advantage of feats that are unexpectedly good in those extra books.
For example, in Complete Warrior, I like the Ranged Disarm and Ranged Pin feats almost exclusively for the cool flavor. Ranged Pin in particular is dangerous, because a DM can "nerf" the feat by merely having all his enemies avoid walls & trees. However, if your DM is a fair player, that feat is a really fun way to stop the bad guy from escaping. Ranged Disarm is also fun in that if you get really good at it, it's awesome to have a high-level character disarm a
room full of bad guys.
I like Shield Slam from the same book just due to the ability to apply something other than hit point damage. I've been toying with allowing Shield Slam to do a 1-round Stun instead of just Daze -- this way a fighter can work with a rogue to enable sneak attacks. It's pretty high level stuff, so I don't think it's terribly unbalancing in concept, although I've not yet tried it in gameplay.
The Combat Brute and Raptor School feats are fun just for the varied attack styles. The High Sword Low Axe is
awesome for free trip attempts. I love the idea of a two-handed weapon master striding amongst foes, knocking them over as he goes.
In the Player's Handbook 2, the Penetrating Shot feat gives a bow-using fighter something similar to a lightning bolt effect -- the shot hits everyone in a 60' line. That's cool, although it's situational. Telling Blow is just crazy-good for a fighter/rogue multiclass character. Especially a rogue with all the feats that make crits more frequent. Combat Panache & Shadow Striker are also good for such a character.
Blood-Spiked Charger is awesome for shield-bashing fighters.
I also allow some fighter bonus feats from the Net Book of Feats. If you haven't heard of that, it's a collection of online custom-made feats that come with balance ratings, so a DM can tell if a feat is a good fit for his campaign. I'll tell you about the three coolest feats I allow from that. First, Bleeding Critical, which allows a fighter to do 1 point of Constitution damage on a strike. I have ruled that the effect stacks, so if a fighter manages to score 3 crits against an opponent, then that enemy has lost 3 points of Constitution, including the lowered hit point totals that it implies.
Second, the feat Opportunity Shot allows bows to be used for attacks of opportunity at point-blank range. This gives a bow-fighter a huge threatened area. Couple this with the Combat Reflexes feat, and you have a Legolas-type that can whip arrows all over the battlefield, many times.
Finally, the feat Riposte allows you an AOO at anyone who swings at you and misses. Depending on the DM, it may be that "1 or more" misses gets you one riposte, or it may be that each miss earns you a riposte. If the latter, this scales up really well at high levels where you could be surrounded by 2 or more enemies with many attacks; you could slice & dice them in retaliation a
whole lot. It can cause a fighter to deal out as much damage to a hostile crowd as a wizard's fireball or other AOE spells.
Good luck. Have fun!