I read that many US pilots complained about the lower firing time of the F4F-4, and that they preferred the F4F-3. (not to mention the performance drop, which the folding wings didn't help either)
4x .50 cal BMG's would have been more than suficient aganst the lightly armoured Japanese fighters and the F4F-3 asnd F4F-4 had the same ammo load, just spread-out in 6 guns instead of 4. It was the Brits who requested the increase in firepower iirc, their European opponents being quite a bit more damage resistant than those the USN was facing.
Plus if you notice, all later Wildcats, FM-1 and FM-2, had 4x guns again... Coincidence?
The Hellcat and Corsair had six BMG (except for the cannon-armmed F4U's) but they were considderably larger too.
But the F4F was certainly important and was the best option the USN had, inless they were willing to use inline engined fighters... (the F2A was decent, but Brewster was in no position to produce it in the quantity and quality necessary, as Grumman was; rember that quite a few USN pilots preferred the Buffalo to the Wildcat, as long as it wasn't at max fuel load/overweight) And for the environment, the F4F was akin to the P-47 in ruggedness, though only by comparison to the Japanese. (overall, the F4F was probably about as tough as the P-40, except for the engine, which was inherantly more durrable)
On the same note the USAAF needed the P-40 and P-39 to stave off Japanese attacks untill better fighters arrived.
The only carrier based a/c in the PTO that could fight the zero in a turn-n'-burn dogfight and that saw significant service in WWII would have been the Supermarine Seafire.