The difference between 3e and previous editions is this:
In previous editions, practically all the min-max decisions were made at character creation. How to assign ability scores? What race to play? Multiclass or not? What kit to pick? If you used the Player's Option: Skills and Powers or Spells and Magic books, what racial and class abilities to buy? The problem was that some choices were significantly (if not obviously) superior to others. However, once character creation was over, the scope for min-maxing was reduced. Generally, it revolved around getting the right magic items. If you played a human, you might try to dual-class. If you played a wizard, you might try to get better spells.
In 3e, min-max decisions take place over the entire course of the character's career. What class or PrC to take next? What feat to pick? Where to assign ability score increases? Arcane spellcasters choose spells known or spells learned. Rogues choose special abilities. Druids and rangers choose animal companions. Paladins choose special mounts. Players thus have more opportunities to make choices, and some will of course be more optimal than others. Overall, however, the difference between the most optimal choice and the least optimal choice is less significant than in earlier editions.
In summary: earlier editions had fewer choices, but the choices are more significant. 3e has more choices, but the choices are less significant. If there appears to be more min-maxing in 3e, it could simply be because there are more choices. Min-maxing will always occur as long as there are choices to be made.