Steam wise I've only gotten into Undertale.. Free to play games wise in general though.. (With linked names if possible)
- Flight Rising a free to play browser game that I currently play all the time (Think welcome week's next week though) - Heroes of the Storm is fun if you're into MOBAs - Hearthstone If your into card games, I could never get too into it myself but I'm not much for card games - Armor Games Also has alot of free and free to play games, all being browser based so no downloads If your into MMOs... I've played a couple decent free to play ones such as Perfect World International and Aura Kingdom
By 'decent free to play games' I mean free to play games where you literally never have to spend money as its either optional content (Such as skins in HotS) or you could save up the free currency to get anything you wanted from the paid store from other players. To me all the games noted (Aside from some MMO based games on Armor Games) fit this to me
Styx: Master of Shadows: About a goblin assassin, focused A LOT around being sneaky, bad combat mechanics but again its all about stealth kills.
Stardew Valley: You are a farmer, take care of your farm, earn money, can even romance some of the villagers and have kids.
Don't Starve: Open world survival, turn off the wolves, you dont want to deal with the wolves i promise.
Metro 2033: Dystopian future where you play as a man stuck under ground with other people having to survive, you have to go above ground to destroy a grove where the monsters nest lays.
Skyrim: This one is self explanitory sense just about EVERYONE knows this game.
Dragon Age: Inquisition: Now im not sure if this one is on steam or not, I personally have it on Origin because of the pack. But it is a GREAT game, free world, dragons to fight, millions of quests to do, romanceable characters, I love this game.
Borderlands & Borderlands 2: Both are great games, another dystopian future setting with bandits, psychos, and other things, another open world questing sort of deal with a primary plot.
Life is Strange & The Wolf Amoung Us: Both are pick your own story and it shapes the plot line sort of deal, LIS will really pull at your heart strings, and TWAU is a very hard case in plot and has you make a lot of hard decisions