Half Life vs Planetside 2
Half Life
Half Life is the first game in the famous Half Life series that has gained a certain amount of infamy among gamers mainly because Valve has refused their fans' request to create a Half Life 3. That being said, the game itself is pretty old - released back in 1998 - and it was a shining gem of a game back in its time because of its amaing gameplay and engaging storyline. Unlike any other games in the 90s, Half Life manages to combine action and adventure along with a what-was-back-then a realistic world into one amazing package. The game also has a multiplayer mode that turns the game's many maps into arenas for you to play against your friends.Half Life is one of "those games" that almost every gamer (midcore and above) would at least have heard of before. It's as classic as classic games go. If you enjoy old-school games, Half Life is probably one of the first few games you'd want to play.
Planetside 2
Planetside 2 is a sci-fi-themed MMOFPS game that's the explosive sequel to its predecessor, Planetside, which was released back in 2003. In a way, the game is more inclined towards the extravagant and yet is still rather down-to-earth mainly because it features massive battlefields where hundreds to even thousands of players can battle it out for their faction. In fact, the game has an exciting gameplay which may bring to mind the games in the Battlefield franchise albeit the futuristic sort.Not to mention, Planetside 2 has an actual war playing out on the map where players who won a certain battlefield will essentially "claim" the land for their faction. The tug-of-war-like power struggle between factions help to bond the players in a way that resembles the deep rift between the Alliance and the Horde in World of Warcraft. The game is also developed by Daybreak Games which is in pretty good company along the likes of EverQuest 2, DC Universe Online and Lord of the Rings Online.
So, if you're looking for an epic MMOFPS game to fully immerse yourself in, then Planetside 2 is your best bet. If not, there are plenty of other casual shooters out there, but you can definitely expect that none of them can measure up to the faction-vs-faction tension, which usually erupts into another battle, offered in this game.