Arena, Daggerfall (bugged out could never finish it, but still played it for hundreds of hours), Battlespire, Morrowind, Oblivion and Skyrim. I never played Redguard or the phone apps.
Daggerfall, Morrowind, Redguard (didn't finish, too buggy on my PC), then Oblivion and Skyrim. I gave Arena a quick try after it was released for free, but I didn't have the patience.
I've said this before, but I got a hundred-ish hours into Daggerfall, and my saves got corrupted. I wrote this long, nasty email to BGS, and one of the devs (Julian?) asked me to send him the file. He fixed it and sent it back.