There are only two real reasons to dislike inFAMOUS before you start really nitpicking. One is that the randomly-generated battles occasionally hit you with a nearly-inescapable catch-22, such as fighting more than one guy at once who has a shotgun. Any situation in which I, as the protagonist, can get stunlocked to death is a point-dockin' offense.
The other is that the plot is straight-up ridiculous, even considering that it's about a bike messenger getting caught in an explosion and waking up with electrical powers. Realism gets kicked to the curb really early on, and that's just dandy, but there are about a dozen things I could question here and I'm not even warmed up. Why do his electrica-based powers include psychometry and healing other people? If Cole can't handle guns without detonating the ammunition, how do his phone and GPS manage to work? Where the hell are the gang members you fight throughout the game getting their endless supply of guns, ammunition, explosives, and grenade-chucking hoverdroids? Who thought that ending was any kind of a good idea?
inFAMOUS actually makes a fair bit of sense for the first few story missions, but chucks it all in for a long drive down First and Insanity around the time your archnemesis shows up. Fortunately, the game itself is a lot of fun.
Sucker Punch is the developer that gave us the Sly Cooper series, which makes sense, because inFAMOUS plays like the world's largest platformer level. Cole McGrath can scale just about anything, within reason, so you can climb just about anything you can see. Just moving across the city can be a lot of fun, because once you hit a rooftop, there's almost nothing that can slow you down. It's closer to that dream of endless motion from the Spider-Man movies, to the vision of a city as an endless playground, than any video game has managed to come, including the games based on the Spider-Man movies.
You begin the game as what amounts to a barely-superhuman parkour runner, and one of the survivors within the quarantined Empire City. Two weeks ago, Cole delivered a package that blew up, irradiating him and killing thousands. In the ensuing riots, a plague broke out, forcing the U.S. government to erect a blockade across the only bridge out of town. Now, Empire City is a gang-infested hellhole with no way out.
Cole's first outing as a "superhero" ends with his being made a pariah by the other survivors, all but blamed for the original explosion. Now, you as Cole have a choice; do you punish these people for doubting you by taking over the city, or do you rise above it and fight to protect them from the gangs? inFAMOUS sort of expects you to go the former road, but doesn't force your hand.
As you restore power to the three islands that make up Empire City, you gradually unlock more abilities for Cole, and eventually turn into a one-man wrecking machine. All of Cole's abilities are accessible at once via controller combinations, allowing for a large amount of flexibility on the fly; you don't have to "equip" any of them, so you have all of your abilities on tap at any time. Granted, some of them are harder to use than others, such as the ultimate "Hero" power, but it manages to give you a large, flexible moveset without forcing you to master some kind of arcane Ninja Gaiden combo system. My only real complaint there is that the bullet shield power doesn't work as well as advertised; machine guns tend to blow straight past it by virtue of sheer projectile volume. Enough hits will get past the shield that you may die anyway.
A few of the usual sandbox-game pitfalls do show up in inFAMOUS, such as truly annoying escort missions and "races" across town. Some of the quest design could have used a bit more fine-tuning, particularly near the endgame when you're supposed to be using the bullet shield.
You can also run into a surprisingly large number of random gang members as you explore the city, up to and including bosses you've defeated. By the time you unlock the final island, the Historic District, the random encounter table includes invisible guys with shotguns, the aforementioned hoverdroids, giant scrap-robot golems that can easily take you out one-on-one, huge illusionary Godzilla-esque goons who try to stomp you underfoot, and ordinary mooks with machine guns and a ridiculous amount of health.
It's not unusual to run into five guys when you're just crossing the street, and then, when you run away to regenerate health before finishing them off, finding three more just standing around in an alleyway. You don't find that many enemies in one place when you're invading their strongholds, but God help you if you go down the wrong street.
That's more along the lines of a warning than an actual point against inFAMOUS, though. It's got far more good points than bad, and is one of the reasons to own a PlayStation 3. A lot of the problems I have with it are just rookie mistakes, and I'm looking forward to the inevitable inFAMOUS 2. I just hope it has different writers.