Warframe...
Has 500+ hours of gameplay (there are players with 1k + clocked hours)
The game is updated by the hour (constant "alert" missions directly from the devs themselves) Events constantly happening, amazing gfx, 100+ enemies each with multiple forms, 100+ levels that are guranteed to almost never be the same (random generation on everything including storage placement, tileset, level, enemies, etc), but heres the best part, 0 toxic people, the moderators actually try and keep all chat clean and strictly enforce things such as age policy, chat restrictions, chat sectors, etc.
+ game just had a huge update adding a whole new ship sector, complete map rework, new enemies, new mission type, and very soon an even bigger update will happen! 030 (major to the ever expanding story of course <3)
100% free, also huge amounts of customization for your "warframes" such as color set, skins, poses, helmets, regalia, sigils, syandanas, and so much more (weapons are also customizable to the extreme)
3 weapon classes (melee, primary, secondary) all with over 20 types of weapons, each unique. (not including prime versions and prisma (both can be recieved in game if ye dont wanna pay for them)
Unlike most games where its "pay to play" every weapon in game and frame can be obtained without spending a single penny (some cutomizations cost money but its very cheap and it is easy to obtain a 75% discount on all purchases)
Pvp, even a new in game sport (which is amazing, wether watching or playing)
Bosses up the wazoo (each planet has a boss, some have multiples)
Even a path to choose for your "warframes" side to be on (over 6 not including later game content, i wont spoil it)
100+ mods to apply, each with different forms and different effects, some event only, some special ducat shop only.
And so much more, all i said is a small portion of the game :3
And as i said, 100% free!