I just finished it too (imported the Japanese version) and my god, i was getting infuriated by the horrible inventory and commodity system (MY GOD ITS FUCKING SHIT!!), the forced coop situation with the insufferably stupid AI, and how ALL the charm and the feeling of being such a well designed and polished game that RE4 had was utterly absent in RE5. This seems to be a case of design by comity (see the number of "Designers" in the credits?) and i believe the producer sticking his nose in WAY too much in the design where it simply does not belong. They seems to have thrown every little gameplay idea they could think of, whether it worked or not. None of the boss battles are all that well thought out and often in many boss fights, i'd be questioning if my tactic is the correct one, they never adequately direct the player in exactly what you must do. Sheva even said "That's his weakpoint" yet the way i killed the boss was a means entirely different.
Also, when the Ganados (yes they aren't Spanish, but it's the best word for them) appeared carrying assault rifles, i was just gob smacked... i simply couldn't believe Capcom did that. Around that time it started going downhill fast, until the final boss fight where over and over i'd run out of ammo and die before finally finishing it off. Even the story, the bit which kept me going to finish it wasn't as good as i hoped. Cutscenes were fantastic (well the whole game looks utterly beautiful, best looking game i've ever seen), but the story was disappointing to me.
Also, i'll say it again, the inventory system FUCKING BLOWS.