The arcane pool feature gives you higher enhance bonuses, and you can further improve yourself with buffs.
Also, that "one extra attack" is going to be a spell, which is often worth more than 2-3 attacks from any other class (even beyond damage, the ability to pounce or buff up while also attacking is pretty great). You can also debuff your enemy with a touch spell, that makes all your subsequent attacks more likely to hit.
The enhance bonus you can add doesn't stack past +5 which a fighter can get with a normal +5 weapon.
I understand the extra attack is a spell, but you have to actually HIT your opponent for it to matter. Granted your first attack is likely to hit but again look at my example...
+27/+22/+17/+12 vs +13/+13/+8/+3
A Magus's best attack is worse then every attack the fighter has other than the last. If a DM balances an encounter to give the Fighter's last attack a low chance to hit.... that means your BEST attack has a low chance to hit... the others are just laughable.
Stuns, Sicken, Flanking, ect... all those things can be accomplished by the other classes by using abilities such as crit feats or augmented by casters in the party. It just seems to me the magus lags behind for a front line fighter type. I have the same issue with Warpriest and Monk