I'm 43. I've been playing computer games since the 1970s. My wife, also over 40, and a few years older than me, probably plays computer games more than I do. About half the members of my World of Warcraft guild (Curmudgeons on Feathermoon) are over 40. My father plays computer games, and he's 77. My mother in law also plays computer games, also in her 70s.
My first computer was a Processor Technology Sol with 16KB of memory. Yes, those are really wood panels on the sides. This predated the Apple II, TRS-80, etc.
Trek-80 rocked. Wow, there's a pdf of the manual here -
http://www.sol20.org/manuals/trek80.pdf
Some other computer games I've spent a lot of time with. I really can't remember them all...
dungeon (which became Zork when ported to Apple II, PC, etc)
Original adventure
An Atari 800 space shooter game that I can't remember the name of
hack
nethack
cbzone, a clone of Battlezone
dragonbane (palm game)
rogue, urogue
ragnarok - this was an old PC/DOS rogue-like game from the early-mid 90s
moria
Wizardry
Angband
Doom
Quake
Civilization and sequels
Alpha Centauri
Diablo
Everquest (eqmac)
World of Warcraft
The Quest (currently playing this on my iPod touch - I had an iPhone at one point, but I decided I needed a device that would reliably make and receive calls)