PlanetSide was one of the first MMOs (certainly the first MMOFPS) I ever got into and it remains to be one of the best facilitators of large scale, competitive PvP gameplay that I'm aware of. I understand that a lot of gamers missed out on it because it was PC exclusive and was released when paying a monthly subscription for a game was a new concept for most people. I am writing this post to inform those of you who missed it and maybe bring you into the excitement for the upcoming sequel.
To put it simply, PlanetSide was sci-fi Battlefield that took place in a persistent open world and went beyond what even Battlefield games allow in terms of player freedom and role choosing. There were no "games" or "matches" in PlanetSide. There was no score. There was just a large planet full of constant action that you could hop in and out of at any time. Battles would often consist of giant 100 vs 100 firefights. Rather than trying to get more kills or points than the other team, the goal was to capture bases and towers across the world, each offering its own perks and bonuses to your faction. Want to grab an air-to-ground assault plane? You're going to need that nearby Dropship Center.
The number of options available for progressing your character was impressive. From tanks, planes, buggies, robotic power suits, various armor types, anti-infantry weapon, anti-vehicle weapons, sniper rifles, hacking, engineering, support vehicles, cargo vehicles...you could choose to gain certifications for all kinds of skills and equipment to spec your character the way you wanted to play. If you wanted to wear infiltrator armor and stealth your way into the enemy command center and hack it right under their nose, you could do that. If you wanted to pilot the huge cargo plane and fly your squad over the base to drop in from the sky, you could do that too. Want to set up turrets and mines to reinforce a building your team just captured? Done.
What really made PlanetSide special was how all of the framework I explained above allowed for truly great emergent gameplay. If you ask a PlanetSide player about the game, they are likely to have all kinds of "war stories" about awesome unscripted moments that happened to them or their squad. I could go on and on for hours about all of the possibilities this game made possible, but I think this video will do a better job showing you what PlanetSide was all about: