People play games for different reasons at different times.

Richard Bartle was one of the first to present a coherent theory about this -  the bartle test. Another researcher, Nick Yee questioned Bartles findings in his daedalus project.

Bartle initially started with 4 player types below:

Achievers
Explorers
Socializers
Killers

Bartle increased his graph to 8 types. He discusses these types at length in this article on his website :

click here to see his graphic describing player types.

Nick Yee had a different perspective than Bartle, and presented the following reasons play mmorpg’s source) :

click here to see his table describing player types

I think people probably are generally one specific player type, but drift into other types as they play.

I think people probably are generally one specific player type, but drift into other types as they play.

Either you and Bartle are both right, or Bartle made a really bad terminology choice when he assigned “opportunitst” as a player type. For, in truth, we are all opportunists of one sort or other, as in…

I believe I’ll take this opportunity to:

Achieve
Explore
Socialize
Kill monsters
(those are Bartle’s original 4)
(here are some others)
Softcode
Prettify/Decorate/Author
Plan/organize an event (LARP?)
(and some less-tasteful realities…)
exploit
bully
disrupt

We’re all opportunists at heart, even the most saintly people to walk the face of the earth (hey, here’s an opportunity for me to help others).