Both flicks are sort of a "Sims taken to their absurd extreme" sort of movies, but from slightly different angles.
Both flicks are entertaining on some levels if you turn off internal questions about "if this tech is available why the heck <insert obvious question here>". Suspension of disbelief is a good friend.
Acting edge goes to Surrogates because of nuances in character portrayal by a great cast - plus Bruce Willis really rocks the Bald with Goatee look, and Radha Mitchell is awesome as always. Bonus: Rosamund Pike.
Action edge goes to Gamer - more explosions and graphic limb severings and head detonations. Bonus: Dexter. Negative points: John Leguizamo in a throw-away role. WTF?
Both movies had plenty of 'jeeze come on like THAT wasn't obviously going to happen' moments. I'm not sure if movie maker imaginations are just too homogeneous these days or what. I guess I kinda expect a little more 'surprise me' than I get.
Overall I liked Surrogates better than Gamer, not sure if that was a cast/performance thing or what. Maybe the whodunit aspect, but don't set your whodunit expectations too high. Regardless, either movie makes a good cheap rental to watch.
Surrogates tech involves remotely controlling robots that look like people; Gamer tech involves people remotely controlling OTHER people.
Gamer tech is way more icky than Surrogates tech. And less believable.
However, both movies feature sweaty fat guys controlling chicks - an obvious nod to the internet today, where behind every beautiful chick (or child hitting on other children) is a sweaty fat guy wearing only a towel and eating cheetos.
One of the most obvious questions brought up by both flicks: Apparently the high-volume data signals required remotely control and receive feedback from 'sims' is not much affected by buildings. Gamer does acknowledge latency problems can exist, Surrogates completely ignores it. Gamer really doesn't address the wetware <-> firmware and power interfaces too well. Surrogates can get away with "hidden inside" - and there's charging stations all over for when your surrogate starts running out of juice.
Don't worry - there are plenty more obvious questions where that came from.
In Surrogates apparently 90%+ of the world population can afford a Surrogate model, abilities of the models vary by what one can afford. And surrogate mailmen deliver mail, so despite the massive numbers of folks logged into their surrogates mostly all the time, not all communication is handled electronically. People commute their surrogates to workplaces from their homes, so jobs still exist. As do police and FBI forces, even though surrogate use dropped crime levels considerably. People still furnish their homes beyond a minimal spartan appearance for some reason, even though they're in their surrogate chair all the time, except when pooping. There are still clubs full of surrogate patrons, and surrogate club bouncers to 'tip' to get in the clubs. People still eat/drink, and so do their surrogates (why???). There are enclaves in cities filled with folks who refuse to drive surrogates, and will destroy any surrogate that comes into their area. Not sure how their economy works. The one they show kinda looks like a hippy commune.
Gamer economy is a little more believable in the context of the world they present - if you don't think too hard about it. That is, one can either afford to pay to control other people, OR one gets paid to be a person that is controlled. Well, except felons (which is the core story). Not entirely sure how the controllers earn their $$ to control other folks, but apparently the economy is such that if one is a have-not one may just have to be a 'sim' to afford to get through life, and have put up with whatever degrading despicable deprived sick fantasies the controllers put you through. I can't imagine anyone willingly continuing to be a "sim" after some of those things people do to 'em.
Either way, either movie has its flaws. Try not to think about 'em too much, just sit back and watch.