Pictures don't make a game, otherwise Doom or Heretic could easily be dismissed as just lame. If you like first person shooters and you configure it right (like I don't use a joystick with it and play it with WASD) then it will be one of the best games you have played. The gameplay itself is great and holds up very well. It is only $3 for each game and would recommend them to anyone who wants a good 3 axis shooter.

Defo Fallout 1&2 Followed by Freespace 2, Freespace and Sacrifice. Fallouts were games that made me appreciate good roleplaying experience ;)

For me M.A.X. 1 and Fallout series. Still waiting for Blood & Magic from Interplay.

MDK Series and Freelancer Series.

just for sheer fun and great sounds bytes... die by the sword and limb from limb!
(Rraaaaaahhhhh Bloody Hell!!!! lol, gets me everytime! )

Freespace 2, bar none.

Fallout 2, but only because Freespace 2 can be had for free.

Freespace 2 legally for free? Where? :P
As for the subject I think the best are Fallout 1, Fallout 2, Freespace 1 and Freespace 2.

I've heard about the source code, but as you said never about the original campaigns and other original features being released with it.

Fallout 1, 2 and Original War. I have played about half of games here though, so I can't be really objective

yeah, this is eaxctly right, you can distribute the engine all you want but the assets that make it a game, not those.
also the thing with the EULA on the installer was an oversight which was fixed and the copy of the EULA the game installed with itself didn't have hat part in anyway. So yeah, Freespace2 has never been freely distributable.

Ah, I've been playing Freespace 2 SCP for sometime now, and by playing I mean the original campaign. It would appear that it isn't just the graphics engine that went open source but the campaign too.
Source: ME &
http://www.hard-light.net/forums/index.php/topic,56245.msg1136788.html#msg1136788
With this in mind it really doesn't make sense paying to play a version of the game that essentially has inferior graphics when a free, better version exists. That is of course unless you wish to thank Voilition for their hard work in bringing one of the best space sims to scene ever. Then again, if Freespace 2 (Engine and campaign) is completely opensource, isn't there a legal problem with (EULA?) a company charging for it?

got to go with Fallout 2 as best game here Freespace 2 would be my second.
There are so many classics here hard to choose

Fallout 2, no doubt about that.