I've only bothered to create two of my own categories: "Stealth" and "Flash". Now, I doubt any of the games I add in Flash were actually made in Flash but I put those type of games... The kind I could find on gaming sites like Kongregate, ArmorGames, etc. Except on Steam they're usually more robust and longer-lasting.
I like Game Dev Tycoon, Rebuild 3, FTL and Windward but they could all easy be on an internet app. (In fact, Rebuild 3 is just a more robust version of 2, which is on the internet).
Stealth is obvious, it's one of my go-to genres. All of the AC's are on there, along with Far Cry, Sniper Elites, Shadow of Mordor. Splinter Cell, some Hitmans, and even Watch_Dogs because it does have a stealthy element to it thanks to the silenced pistol.
I could use more organization. I sometimes sort by "Recently played" to see what I've been in the mood for in the past month or two. Sometimes I scroll down and look at all the uninstalled and "hours played" and see if anything strikes my fancy. There's a lot of stuff I got during some super sales and didn't bother to play more than 20 minutes of.