I'm playing RE6 now and my biggest complaint is one that I haven't seen too many people gripe about. It's the padding. This game is stuffed to the gills with padding. Everything seems designed to take as long as humanely possible:
-- the chapters just go on too long -- too much repetition between storylines (e.g., refighting same boss as Ada) -- all the enemies are ammo sponges and take forever to kill -- just how many shots does it take to kill Leon's endgame boss?
I've only finished Leon's chapter and done 1 or 2 episodes with the other 3 characters and it's almost like Capcom is just DARING me finish it without getting thoroughly sick of the game.
Sounds like you're not making much use of the melee and stealth.
Especially in the Leon chapter, if the enemy hasn't spotted you, you can perform a free melee maneuver that will normally kill the enemy 90% of the time.
This might not be for everyone but counter attack melees can really save ammo, since they almost always instantly kill the enemies.
You can also make use of the remote control explosives to take out a lot of enemies. The good thing about these explosives is that you can plant it while sliding. Sprint into a crowd of zombies with the explosives equipped and press the L1 button to slide and you will plant the bomb the same time you slide. Run to a safe distance and detonate the bomb.
It's going to get tougher in other chapters but you really need to learn a lot of techniques, since this game isn't all about emptying clips into enemies. --- My thoughts about Bioshock Infinite: http://tinyurl.com/mn5ll4x (WARNING: CONTAINS SPOILERS)