I can possibly see Starbound taking over TF2 in the coming weeks/months. Ark could climb when that game is finally finished.

I'm primarily a console gamer so excuse the playtimes

1.Neptunia rebirth 1 - 60 hrs
2.NARUTO SHIPPUDEN: Ultimate Ninja STORM 3 Full Burst - 52 hrs
3.Melody's Escape - 43 hours
4.Neptunia Rebirth 3 - 33 hours
5.Storm 4 - 29 hours
6.Neptunia Rebirth 2 - 24 hours
7.Dariusburst Chronicle Saviors - 24 hours
8.Undertale - 23 hours
9.Neptunia U - 17.2 hours
10.Melty Blood Actress Again Current Code - 16.3 hours
11.Guilty Gear Xrd - 12.5 hours
12.Tabletop Simulator - 11.9 hours
13.Last Remnant - 11.7 hours
14.Neptunia VII - 9.6 hours
15.Ninja Blade - 9.5 hours
16.Astebreed - 9.1 hours
17. Skullgirls - 8 hours
18. Necrodancer - 7.9 hours
19. Eternal Destiny - 7.4 hours
20. Trails in the Sky - 5.9 hours
21. King of Fighters 98 - 5.8 hours
22. King of Fighters XIII - 5.6 hours
23. Symphony - 5.4 hours
24. Code of Princess - 5.1 hours
25. eXceed 2nd - 4.9 hours

I don't know how you guys all posted it :(

My Profile playlist: http://steamcommunity.com/profiles/76561197990367374/games/?tab=all

Top5:

Spent some big hours in a few games but others are fairly modest :)