I have played more than one game in more than 5 video game series.

Star Control
Fallout
Half-life
Earth 2150-2160
Space Empires
Medal of Honor
Age of Empires
Doom
Blitzkrieg
Stronghold
Call of Duty

Also, would the Total War games count as a series?

I don't know, but I used the Wikipedia list of video games series to decide if the video games I played were parts of series: http://en.wikipedia.org/wiki/Video_game_series . So yes, I guess.

Megaman is probably my favorite series out of all of them, what is yours?

That would be difficult. They were all good for different reasons.

Hmmm....

Stronghold, Fallout, and Half-life are the top three.

Lets see..

Final Fantasy
Pokemon
The Elder Scrolls
Halo
Half-Life
Kingdom Hearts
Dark Cloud
Mario
Donkey Kong
Guitar Hero
The Legend of Zelda

Holy fuck! I forgot about X-COM!

Your xcom experience must have been vastly different than mine, then. My xcom experience was remembering being good at the first from a few years ago, starting up the second on the hardest difficulty, and having my ass kicked so hard my computer broke down. I don't think that counts as 'playing'.

I always played it on the hardest difficulty level. And if that wasn't enough, some of the aliens had been modded to be extra perceptive or have additional abilities.

It was fun. Even if only half of the troops made it back to the lander.

I beat X-COM 1, but X-COM 2 [not modded for extra powerful aliens, because the aliens in that one were just as powerful to begin with] apparently broke somehow and I was unable to research the advanced submarines needed to get to the alien command base.

I was able to destroy every alien base that materialized around the world, and I made big globs of money, but I couldn't actually win because of the damn broken technology tree, which pissed me off.

There you have it.