The perfect formula, for the perfect online experience.
Return to Castle Wolfenstein (RTCW) had an amazing multiplayer. ET simply expands on that gameplay but keeps the overall premise the same. There are a few changes. The maps are generally larger, there is now a XP system, the sounds have changed and other minor changes such as graphics and classes.
The thing that makes ET great is it's gameplay. The shooting and moving is non-realistic but it isn't like quake. For me, it's perfect. The action can be fast paced but it isn't simply a run and gun shooter.
Another neat thing about the gameplay is the entire objective idea. For every map, there is some sort of goal (kind of like assault it Unreal Tournament) that needs to be accomplished. Normally there are several other objectives needed to be done in order for the final one to be accomplished.
This is where the class system comes into play. There are 5 different classes, each has it's different uses. Engineers are normally the one's that deal with objectives, while medics keep the team running and the enemies back at bay. Another thing that goes along with the class system, is the XP system which is a really nice touch to the gameplay. As you play longer on a server, you'll eventually gain bonuses (similar to No One Lives Forever 2).
It's this entire formula that makes ET. Whether it is just going rambo on the whole opposite team or maneuvering through the objectives as a team. It works amazingly and you can tell the difference from someone who hasn't been playing it then someone who has.
The only real problem with ET, is that it isn't really finished. The game was incomplete when the cancelled it and from the original download, you'll notice some bugs. Patches have come out to fix some of these but what is really important are the mods. Not the total conversion mods but the one's that adjust the gameplay of ET by just a bit (ETPro, ETPub etc). These include several changes, bug fixes, cheat prevention and are geared for a certain amount of audience. For example ETPro is meant for people who like to play the game seriously while ETPub is meant for people who want to play for fun.
The game comes with 6 maps. With the exception of one (railgun but some people enjoy it) they're really well done. But what really gets the game going are the custom maps. You can play with 4 original maps and then add another 3 custom ones and run them on a server and it'll be enough. Each map runs for a long amount of time which is good. Time limits can be anywhere from 15-30 minutes. There is also a respawn time, which is a plus, it isn't like Counter-Strike where if you die, you need to wait for the map to finish. You can get back in the action in just seconds.
The engine is based on the Quake 3 engine. This is actually a good thing since this opens room for trick jumping and so on. The Quake 3 engine is really modifiable and allows great use of the config. The problem, is that the graphics are out of date. Keep in mind this game was meant to be an expansion pack for a 2001 game. The graphics are supposedly better but in my opinion, I think it just slows down the game more so from RTCW. The one difference is that the maps are larger and the outdoor areas look nice but don't expect to be amazed from this game's graphics.
The sound has been changed from RTCW and I'm not too sure if it was for the better. The gun sound changes are actually maybe worse from RTCW. Other effects such as explosions and walking are on key, though.
Overall, this is a great game, for a great price. It's totally free and its a 250 meg download which is less than a lot of game demos these days. It's the best free game out there and it's defiantly the most popular free game. In a way I almost wish it was completely finished (but then if it was released it wouldn't be free...).