I've done a lot of PFS... where we basically have to run things by the rules. We don't get the luxury of fiat'ing encounters or the such to make the non-wizard characters feel better about themselves. And players know that.
And many, in PFS, just make what, in their mind, is the most powerful build they can find. It seemed to me that nearly half of the players focused a lot of optimization and squeezing every last bit of combat effectiveness out of their builds. They wanted to dominate.
Yet, I didn't see all that many pure arcane casters/builds. And, I even saw more than a few martial builds.
I won't argue whether or not wizards/arcane casters are the key MVP in or out of battle more often than martials. I think you can make a solid case either way. But, in PFS, where players don't really get to have long discussions at all about party balance (you basically show up with your character and go for it), I rarely had two arcane casters. I often had none! So... while they may more powerful or dominating (especially when played well), I just don't see a swath of people flocking to them. :/
Even in homebrews, where party members discuss roles and balance, ya just don't see a lot of times where two players but heads over who gets to fill that arcane role. I couldn't tell you why, but its often harder to fill than the cleric/healer role nowadays. So, if they get to be OP'd in some battles where they prep properly and know what tools to use and when to use them...well, that's OK :)