Prototype is a game I would only play if I was in the mood for excessive gore in a sandbox environment. Don't get me wrong, it's a great game. This game is very good about immersing you in the environment, and there are tons of blood, but I found the AI too easy to fool, and the story is lame.
The artificial intelligence (AI) of the non-player characters (NPCs) is as artificial as ever. Unless you're fighting a boss or a very powerful character, the enemies will just run up to you and punch/swipe. The enemies with guns just stand around, making easy targets. Furthermore, most of the characters are too dumb to recognize Alex Mercer, even after he slaughtered their friends, as long as the stealth meter is empty. This makes sneaking around absurdly easy.
You can play either Easy or Normal difficulty. After beating the game, you have access to Easy+, Normal+ and Hard and Hard+ modes. The "+" means you get to keep all your stats from a previous game save. This makes the game painless to replay. I have not played Hard mode yet, so maybe the AI gets better.
The story would be the lowest point to this game, if the AI wasn't so stupid. The plot centers around Alex Mercer, codename Zeus, and involves a killer zombie disease. Yeah, it's a zombie game with super powers. The story could be entertaining, if it was told well, but it isn't. After a while, you might find yourself skipping all the cutscenes, because they're just boring. Some scenes look very cool, though. You're basically just regaining lost memories throughout the game, so it isn't really an interesting story.
A lot of the visuals in this game remind me of the Spider-Man games. You're trapped on an island in New York City, and while this is only part of the city, it's plenty of space, but the bridges have dead ends, taking away some of the immersion. So yeah, there are boundaries or invisible walls, but they're hidden fairly well.
There are blue and pink orbs scattered throughout the island. The blue orbs are Landmark Orbs and simply give you EP or evolution points. The pink orbs are Hint Orbs and give you a helpful tip and some EP. EP can be collected from practically everything you do, and it can be spent in the Upgrades menu. You have many upgrades to choose from, and you'll unlock more upgrades as the story progresses.
You can also unlock minigames as you purchase upgrades. Each minigame can give you one of three medals, bronze, silver or gold. Once you have a gold medal on all minigames, you can also try for a platinum medal. Some minigames are extremely hard, while others are extremely easy, but they're usually fun, anyway.
Besides the poorly told story and the extremely dumb NPCs, this game is pure fun. I enjoyed running on walls, gliding through the air, unlocking abilities, finding hidden orbs, and slaying a variety of very tough enemies while crowds of zombified citizens cause mayhem in the streets. I highly recommend this game.
Popular question: Infamous or Prototype?
If you're a PS3 gamer, you have access to Infamous, which is a better experience in most ways, but these games do not offer the same style of gameplay, so they are both worth picking up. Infamous is a third-person shooter similar to Tomb Raider, with some Crackdown mixed in. Prototype is also third-person and has similar movement controls, but it lacks the shooter element. Prototype is more like Spider-Man and features a more inhuman ability to scale buildings and jump extremely high. They're both fun in their own way.