For a brain game to be good for your brain, it has to stretch your gray matter. If you play Sudoku, for example, and it becomes more of a compulsive meditative thing than a challenge that you are wrapping your brain around, then you are wasting your time. You'll know when a brain game (and any game) is improving your brain fitness when that game is interesting. When your curiosity is sparked, your brain is developing new connections and that is what keeps it healthy and sharp.
In other words, any game can be a brain game as long as you are engaged, interested and learn new things. Take card games as an example: Bridge and Poker are great brain games. In each game there are new situations and you are trying to figure out what people have in their hands based on their bids. Blackjack is not a very good brain game. Once you learn the rules for playing, you should really not drift from them. Blackjack becomes "robotic" after a point.
So find games for your brain that are always changing and draw on multiple levels of your brain (guessing probability, doing math, trying to read minds, memory, etc.). Once they start feeling "robotic" it is time to switch to a new game.
Here's a few online and offline brain games to get you started.



