Very few games have had more controversy and mixed opinions than Resident Evil 5, and for just/unjust reasons. Resident Evil 5 as you guessed it is the 5th numbered game in the Resident Evil franchise, and with it Capcom decided to test some new things out. Some worked, some fell short, but in the end Resident Evil 5 succeeds in being one of the better games of this console generation.
Resident Evil 5 ran into problems this gen for one major reason, the Resident Evil franchise now has serious competition. Silent Hill has always been around, but after part 2 things went downhill for the Silent Hill franchise, and they've never really been able to recapture that feel again. But along with the new consoles came two new games to thwart Resident Evil's reign. First Dead Space a survival horror/action title, and Left 4 Dead a new extremely entertaining cooperative zombie survival game. The problem that these games bring is that they do things better than Resident Evil does. Dead Space does survival horror better, and Left 4 Dead does co-op action better, leaving Resident Evil 5 on the back burner. But fortunately there are other redeeming qualities that help Resident Evil 5 push from behind and stay competitive.
Graphically Resident Evil 5 stands among the top tier of best looking multiplatform games (so does Dead Space). Resident Evil has a great lighting system, great character models, and great atmosphere. Being in Africa really separates it from the competition, however, I would have liked to see more African cities and wildlife (Zombie Lion FTW).
Resident Evil also has a nice leveling system for their weapons (so does Dead Space) which adds a layer of depth to the game that your typical Zombie shooter doesn't have.
Finally Resident Evil 5's co-op separates it from the competition. Left 4 Dead has 4 player co-op compared to RE5's 2 player co-op however, RE5 is more team based than Left 4 Dead. You really rely on your partner from start to finish, tossing guns, ammo, and health to one another as well as solving puzzles and defeating bosses together. Resident Evil 5 is a true co-op experience from start to finish.
Which brings me to the negatives. Co-op. Yes the very part I enjoyed the most is also one of it's biggest letdowns. Co-op is great, but thanks to co-op the horror element of Resident Evil is GONE. The game isn't scary at all, and the only fright you may get is a zombie sneaking up behind you.
However, the biggest complaint has to be the gameplay. If you've played Resident Evil 4 you'll be right at home in Resident Evil 5, for better or worse. What worked last gen, doesn't quite stand up in this day and age. Not being able to "run and gun" shows how archaic RE5 is compared to other games. The controls are a let down as well. The default choice of controls is probably the worst layout I've every played in a game. If you want to play as close as you can to a standard 3rd person shooter go to "Type D", as soon as the game starts.
Overall Resident Evil 5 is a solid game, it does a lot of things really good, and has a couple of great moments, but overall it just falls short of being what I, and I'm sure most people wanted and expected. But that doesn't mean it's a bad game by any means. The gameplay needs to be modernized, and horror needs to be added back into the formula, but these are things to fix in Resident Evil 6. So judging RE5 on it's on merits nets it in the upper class of good games this gen. The thing is you need to go into RE5 expecting to play a good co-op game, rather than any previous Resident Evil experiences.