Real-Time Strategy (RTS) is always a good genre to play, especially when you have many units to choose from.
I used to play SAGA, an RTS that features several factions where you make a "Nation" based on one of those factions.
Now, I play BattleForge by EA Games, which is a free-to-play RTS but you can opt-in for a free premium account. You also need to buy 'booster packs' to upgrade your 'card deck'. A good choice if you have the extra cash to play but for an average teen who doesn't have the money, then you're basically playing against premium accounts on your free one.
A relatively large download is required, however.
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There's also a quite interesting RTS that I've been playing for some time. It's called
AntRush, and it's a free-to-play ant RTS that features an offline campaign mode, or online play with other players or Artificial Intelligence (AI) or "Comps."
AntRush has four playable ant classes (Gliding, Leafer, Slave-making, Termite), each with its weaknesses and advantages.
The community is relatively small with a few active players. The development has been slow recently but it's still alive.
Maybe this post will help bring new players there, haha
A very small download is required; this game is not CPU or GPU intensive.
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BattleField Heroes is a shooter game that I'm also playing, when I get bored. It is also by EA games.
Edited by harrison858, 18 June 2011 - 08:02 PM.