RE is almost a straight rip-off of BF2, but contains some innovations that make it good fun to play.
Players joining a server must pick a class, choosing from a list that is partly standard fare and partly innovation. You have your four basic classes - Rifleman, Machine Gunner, Demolitions, and Sniper. Added to these are the Squad Leader and Platoon Leader, placed in positions of responsibility over other players. Then the two most interesting classes, the ABE and the Battle Hacker. The ABE, armoured battle engineer, is the game's tank, able to carry four heavy guns, and with lots more health than anyone else. The Battle Hacker is a great new class, who comes with the ability to hack into enemy turrets and mines to 'convert' them to his own side.
There are some key differences aside from the classes. RE is set in the future, not the present. (This might mean I should compare it to BF2142. I haven't played it, though, so I'll talk about what I know.) The developers of RE have gone for a plausibly realistic future scenario, in that all the technology in the game is 'based off current military research.' All soldiers are armed with an awesome exo-skeleton that provides seed, strength, and armour - sort of like Crysis, but less AAA. With the exoskeleton powering you, you can perform super-run and super-jump moves, and (a personal favourite of mine) kick through walls.
Okay, so what does all that mean? Is it fun to play?
In my opinion, yes. The gameplay is not revolutionary - in the most common game type, you shoot the enemy in an attempt to capture flags on the map. But the little touches like the Hacker and the power abilities make this gameplay more refreshing, and make each battle more different. The few times I played BF2, I found myself getting bored of doing basically the same things each time. In RE, there are many different ways to move across the maps and surprise your opponents. The maps are very conducive to this, featuring multi-storey buildings with plenty of ledges to jump on. In a given combat situation on a given map, there are any number of ways to try to eliminate the enemy - go prone and go for the headshot, leap onto a roof and try to get the drop on them, jump over them and shoot from above, or simply sprint the other way and try again later.
Adding to the complexity are the semi-destructible environments. Some walls designated as breakable can be destroyed by grenades or heavy weapon fire, or by kicking them down (or hitting them with your handy dandy sledgehammer). This again opens up tactical possibilities - if a street is being covered by an enemy sniper, you can (sometimes :P) bust through a wall and advance along the street through the ground floor, out of sight. Once you get to know the maps, it's also great to surprise enemies by breaking down a wall on their flank or to the rear.
Aside from gameplay benefits, it's just a huge rush to play as an ABE, with your twin autocannon, and kick down a wall, then blaze away at whatever's behind it. You get that 'I AM DEATH INCARNATE' feeling.
The Battle Hacker brings another dynamic to games. Levels often have stationary turrets placed at key locations like inside bunkers or around flags. The hacker can attempt to convert these turrets by solving a logic puzzle, where a tree of logic gates (such as AND, OR, XOR, etc.) must be manipulated to output a true value. Once this is done, the turret will automatically fire on enemies. Hackers also have the option of turning turrets off, self-destructing them, or having them 'sync' their fire, so that the turret follows your aim.
A good hacker can be a significant boon to his team, given how powerful some turrets can be. Given that the capture-the-flag mode is all about controlling area, turrets help your team no end. When you are the hacker, it is a pure rush to finish the logic puzzle before the timer goes, or before your hiding spot (you're hacking from a secure location, right?) is compromised.
The game's graphics and sound aren't top of the line, it's true. Soldiers and weapons are modelled and animated well, but shaders are limited to a bit of specular, so you won't get the sort of detailed graphics that you're used to today. The environments are very well constructed, and come in two flavours - those set in a destroyed Paris (with a very impressive wrecked Eiffel tower) and those set in the Chinese city Fuijan (Fujian?). Paris is my favourite location - the tall, claustrophobic streets offer plenty of climbing opportunities, and there are always plenty of breakable walls, blind corners, and sniper perches. Again, the maps aren't super-detailed, but there is enough rubble and debris to give the impression of a world torn apart by war.
The game's sound is passable, but not extraordinary. Weapon sounds are quite ordinary but there is variation, ranging from the wussy American assault rifle to the booming ABE automatic grenade launcher and the harsh whoosh of the rocket launcher. Bullets whiz past quite nicely, and air strikes scream a warning.
That said, the game lacks some atmosphere. This may be common to many games, but your allies (real people, in this case) are quite silent. Orders are given through a pure visual interface, and there is no battle chatter. This and the lack of gore conspire to make the battles feel somewhat clean and sterilised (which is quite at odds with the way the environment gets bashed up over the course of a game).
Speaking of bullets whizzing past, that's a sure sigh you'll want to run for cover - because in RE you die very, very quickly. Despite the amazing exoskeleton technology, you're no Starship Trooper: a handful of bullets, or just a couple in your head, is enough to kill you. You do have a one-shot full-repair medkit, but combat encounters are very brutal and very brief. This can put off new players a lot, but as you get more used to the game, you come to understand how to stay alive - stay in cover, and be on your guard.
Ordinarily, I wouldn't bother with this game (if exoskeletons didn't tickle my fancy so much). However, there is one great thing to be said for it - it's *free*. I believe that makes the cost/benefit of the game quite favourable, despite the hefty-ish download (1.3 gigs).
In conclusion, I'd recommend this game to anyone who likes online shooters, but wants some new ideas. Or to anyone who likes science fiction. Or exoskeletons. Or whose wallet is as empty as mine.