This is one of the oldest debates in the RPG community. It is generally referred to as the “tier problem” or “martial characters suck” or something like that. The problem generally stated is that in terms of game balance for games like Pathfinder, spellcasters are simply vastly more powerful, versatile and interesting to play than purely martial characters.
I tend to agree with the general idea that casters are much more powerful than martial characters. I don’t necessarily think this is a problem. I tend to be of the opinion that mastering the awesome cosmic powers of the universe should make someone more dangerous than swinging even the most amazing pointy sticks.
On the other hand, I think that the game as it is today, with the spells and abilities of some classes, the disparity is truly vast. Spells like “wish” or “time stop” or “miracle” are simply power on a completely different scale than anything a purely martial character could produce.
There are variants of the game which attempt to address this disparity, including “low magic” variants and third party or gamer community options like the “E6” rules.
When I look at literary characters that are commonly considered to be awesomely powerful, it strikes me as interesting how limited those famous literary characters actually were. Merlin was basically a fortune teller with some shape-shifting powers. Gandalf never did anything more impressive than a few fire-based spells and some minor healing.
In some respects I believe the game would still favor spellcasters significantly over martial characters if nothing changed except the existing spell list were capped at, say, level 4. Maybe even level 3.
I’d be interested to get the opinions of folks who visit this blog on this question.