Games like Flappy Bird and Angry Birds are pointless retarded games that ruins your focus and wastes your time. Games like minecraft and League of Legends actually help you with memory and coordination. League is a very teamwork based game and isn't like CoD where everything goes well if you kill everyone.
There is a research conducted by APA ( American Psychological Association) that suggests playing video games moderately can help improve cognitive skills and memory. While playing video games, we might also train our ability to focus, plan strategies and react quickly in different circumstances. Very often, kids who play games since their early childhood have a more developed brain than the ones who don't. But of course, everything has to be done with moderation.
I am only voting no as I do not believe it is 100% yes. The question is too broad, in general, it is bad for you, you sit in front of a screen, killing your eyes and depending on where you sit and the console you play, there are other medical conditions you can get like RSI.
That said, if you play the right games, then mentally, yes they can be good for you. They can help your focus, memory, reflexes and they can even teach kids.