I like simple games. So my two faves right now are Reversi and 4-in-a-Row from Tafasa. And just checking their site, Dots is free. Off to get another one from them.....
Edited to add: Deleted Dots. While I don't mind ads in the game, it is too easy for me to scroll a bit too far and engage the browser to take me to their site.
I only have three games on my BB right now, the standard Brickbreaker, Bejeweled, and Mahjong Soliatire, and I get into moods where I'll just play one for a while, then forget it and go with another.