Elevate is great, it has a lot of brain exercises. I prefer the math ones the most, because they are actually very useful for training quick calculation. Language ones are very useful too, specially if your native language is not English. All the other exercises are good too, IIRC. Peak is nice too, it has some different exercises, but some of them are more for speed reaction than actually mental training. I also use Duolingo daily (more than 900 days streak now), learning languages is great to develop your memory and is often times useful.
Games for training brain

Hey BardoVelho! I'm fully agree with you, great message I'm actually playing Elevate too about 1 year and I wasn't expected somebody here is also using it. Second my favourites are some sudokus and chess especially on this site
Hey guys =)
Do you even play other games to train your brain (not chess)? Which ones do you prefer and why? =)