As a fan of single-player gaming, I have to admit that I was more than a bit skeptical when I heard that RE5 would include co-op. I like co-op, but have a hard time finding someone who'd be willing to play through the entirety a game's campaign with me. I tend to keep odd hours, so finding someone I know to play with at 3 a.m. can be a bit tricky. When the game finally came out, it seemed as if my worst fear had come to fruition, with all of the internets a roar about how RE5 was an epic failure as a single-player game and hardly worth playing. I can now say, with great pleasure, that RE5's single-player is hardly the epic failure it was made out to be and is still a heckuva lot of fun.
Sure, the partner AI isn't great, but it gets the job done. While Sheva is not going to pull off any complicated maneuvers, say toggling between different weapons in her arsenal the way a real player might, she's still perfectly serviceable. If you keep her move set limited, she gets in the way surprisingly little and can add a lot to the combat. Personally, I always limited her arsenal to a handgun and a machine gun with a couple clips of ammo for each. She'd default to the handgun, and when out of ammo for it, she'd switch to the machine gun. Complex? No. But hardly game breaking. Just give her a tad bit of ammo and she'll stay out of your way, as well as carry stuff for you. While she has the tendency to waste ammo and health, she's also a damn good shot, so it's kind of a wash (though far from a travesty). I still would have preferred they kept it a strictly single-player affair, but the partner AI is hardly as big a deal as some are making it out to be.
In fact, in a lot of ways, she really added to the game for me. Though it's easy to put RE4 on a pedestal, lest we forget that roughly a third of that game consisted of escorting the defenseless Ashley around? At least Sheva can fight back. And while it's true that she uses up ammo that would otherwise be yours, I found this sort of liberating as I was less conservative about hoarding ammo as I knew she'd use it all anyway. Not to mention the smaller inventory you're allotted in this game. Maybe I'm just indecisive, but I recall spending a long time deciding what to do with my inventory in RE4. Here, I felt like since I had less control over it, it wasn't something worth stressing over. While I'm sure that says more about me than the game, it's sort of a happy accident and I wouldn't be surprised if others have a similar reaction.
In a lot of ways, I'd say this is more a true "survival" experience than RE4 (though maybe not so much horror). While there is a much greater emphasis on action, you also have a much smaller inventory, so ammo is a constant issue. You only have 9 inventory slots, so I'd tend to keep five weapons, plus the melee and bullet proof vests, so that would only alot me an extra 2 spaces worth of inventory. I'd frequently only have room to carry whatever ammo I has in my guns at the moment, and only and extra clip or two stocked up. I'd give a bit more to Sheva, but she also had 3 guns and 2 vests, and was in charge of healing supplies. As a result, I felt like I was constantly just getting by.
The inventory system does have some of what I would consider universally agreed upon flaws. Notably the fact that if you're out of ammo for a gun, find ammo, but your inventory is full, you cannot pick it up just to reload. You can't even set an item down, pick up the ammo, reload, then pick the item back up, as it will have disappeared into the ether. They should have allowed you to automatically pick up however much ammo you can fit in your clip, without it interfering with your precious inventory space. Also, there's no option to make Sheva drop an item. If you want her to get rid of say, a flash grenade in exchange for an herb, but she's out of space, rather than being able to tell her to drop an item, you'll have to swap items with her, drop it yourself, then take your item back. Not cool.
Still, despite some niggling inventory control issues and simple (yet effective) AI, RE5 has a very distinct flavor of action unlike RE4, or any other game I've played before. I'd be tempted to call it a mix between RE4 and Gears of War in its mechanics, but it also brings to mind the earlier Resident Evil titles. The controls are not up to task, but that adds a certain level of tension. Ideally, I would have preferred smoother controls where they could have created tension in other ways. Bioshock is a perfect example of a game that has smooth controls, no penalty for dying, and yet is STILL scary. Thus, making things scarier is hardly an excuse for control quibbles, but for those who liked the cumbersome nature of the earlier Resident Evils may find some redeeming value in the way Capcom chose to handle things.
The game is still far from perfect. I could have done without the zombies with guns sequences late in the game (also true of RE4, mind you). The bosses are certainly a step down from RE4 as well, where half of them suffer from the same design mantra of, "cover it with a thick layer of black worms and it will be scary." And yes, the AI is flawed (but not broken).
Nitpicks aside, the core experience of being in a large area, non-zombies surrounding you from all angles as you desperately try to avoid them, whilst scurrying about in search of ammo, is every bit as intense and fun as it ever was. Go on, enjoy it!