If you want to think of it logically; there is no such thing as multitasking. So I am playing Tomb Raider at the moment but I might go back to playing my Dragon Age game that I am currently trying to finish. But around the 11th of February I will be playing Lightning Returns Final Fantasy 13. It is impossible to be playing 3 games at the same time. The human mind doesn't work like that. That is why they banned cell phone use when driving. Most people would forget about what is on the road and concentrate on the conversation and holding the phone up to their ear.
You stop one action and replace it with another action but clearly you are focus on doing one thing at a time!
Balancing two games seems to be my limit. When popping in The Legend of Zelda: A Link Between Worlds during the Holiday season rush I was also concentrating on other releases such as LEGO Marvel Super Heroes on the PlayStation 4. If there's one game that has an extremely strong narrative though, I don't really like having to swap between more than one game. If you fall behind in the story - which is something that has happened to me in RPGs such as Tales of Graces f - then you sort of have to play catch-up and maybe even replay from an older save just to remember what you were missing.
I try and keep it to two but that can he hard with the lineup of games we have for ps3 and now ps4, "Gotta have that..maybe this....oh yes this for sure!" Is usually what happens going into a store that sell's games.