Ogre Mage said:
A couple of reasons for the unpopularity of the sorcerer come to mind:
1. The class mimics the wizard too much. They share the same spell list and their abilities overall are too similar. The only real difference is one uses a spellbook and the other doesn't. In contrast, if you compare the druid and the cleric, while both are full progression divine casters, they have separate spell lists and their flexibile abilities allow each class to have its own niche.
2. The class lacks synergy.Sorcerers need charisma, but charisma does offer them any significant synergies to their abilities outside of spellcasting. In 3.0 they did not even have any charisma based skills. In 3.5 they have ONE -- Bluff.
3. Lack of support from WotC and third party material. Most of the stuff published on arcane casters is about wizards.
I don't think the sorcerer is really particularly less powerful. They can use metamagic feats on the fly for significant power with minimal cost (so they lose a move-action, big deal). They can certainly be combat monsters, especially once the levels have gotten up there. "Oh, that Disintegrate didn't work? Here's another. I got plenty more..." But therein, kind of, lies the rub.
I think that WotC designers of 3E/3.5 have fixated a bit too much on the combat power of the classes as far as achieving balance at the expense of other kinds of balance such as screen-time balance. They may shine in combat, but are decidedly unflavorful anywhere else and, I think Ogre Mage's points above identify why.
There's little to distinguish it from the wizard and little additional support has been given. The skill point parity between the two seems especially staggering because the wizard is sure to have a significant intelligence bonus. Talk about synergy. The sorcerer may have to scrimp a bit on intelligence and fall way behind in skills. Skills, for the most part, are relatively unlikely to make a huge difference in combat for a major spell-slinger, but they can make a difference in balancing overall screen-time for a character.
I like the way Charisma is used in 3E/3.5. It may be marginally less powerful than some of the other stats I don't think it needs any fixing. It's a stat that has teeth, not for all classes, but for a few where it really should matter (cleric, paladin, rogue, bard, and to a lesser extent ranger and druid if they want to be really good at animal empathy). It's the class that needs fixing.
But as I said, it's not the combat power of the class that needs any fixing. It's the role-playing/how the character can build a niche/flavor aspects of the class that need the fixing.