Hearthstone is a great Collectable Card Game type free-to-play game. A lot of the top players were pros in faster-paced games, like DotA and Starcraft, before switching over. It's pretty fun and fairly deep. I've been playing for about a year. Twitch gaming skills peak at a pretty young age (as young as 25 or earlier) anyway, so switching to something slower is, in some ways, a natural progression anyway.