Unreal Tournament 2004 is the only one I make sure is installed constantly. The rest are games I haven't finished yet.

Never uninstalled since the day i bought them because they are my favourite sims and i keep playing them frequently:

☆ Grand Prix Legends (since ~2001)
☆ Nascar Racing 2003 Season (since ~2010)
☆ Richard Burns Rally (since ~2009)
☆ GTR 2 (since ~2007)
☆ Power & Glory 3 (since ~2008, v2.0)
☆ Falcon BMS (since ~2012, but also vanilla F4 before that)
☆ IL-2 Sturmovik (since 2001)
☆ Microsoft Flight Simulator 2004 (since ~2009)
☆ Kerbal Space Program (since 2016)

Aside from all the above sims, there are also some other permanent residents in my HDD:

Age of Empires II, StarCraft, Anno 1404, Alpha Centauri, Command & Conquer: Generals, Lord of the Rings: Battle in Middle Earth II, Crusader Kings II, Heroes of M&M III, Atlantic Fleet, Banished, Into the Breach, NEO Scavenger, Risk of Rain, Curious Expedition, Tales of Maj'Eyal, Papers Please, Eufloria, Battle for Wesnoth, Open TTD.

As for your games, i'd suggest you to keep Crusader Kings II because not only is it highly replayable, but there are also some great mods for it. Aside from this, i'd keep NWN (for the custom modules), Banished (a lot of replayability) and FTL (same as above). I used to keep this installed for years after i've finished the campaigns, mainly because of the Skirmish mode -- i loved that mode back in the day.

I'd add the number of mods one can install, a time-consuming process that can be tedious to do it all over again should the need to replay them ever comes.

I always keep my GOG games installed on my PC at all times, but there are still games that don't make the cut. I have a large library of games on my hard-drive, but I also have a large library of games in my hidden folder on GOG.com.

Not surprised at all at that first list - we've been missing your screenshots in the other thread :)

It was epic, no other word for it. And if you could get a few players together for multiplayer it was a total blast. A favorite map was the one where everyone played as marines trying to reach and defend a bunker in some alien infested valley. Ah those were the days.

If my memory serves me right, the map was called "Derelict". Unfortunately i didn't have the pleasure of experiencing AvP in multiplayer myself. :(

I haven't been very active lately, but i suppose i should pay a visit there and post something interesting; maybe something from BMS (just yesterday i was doing a patrol over the Korean peninsula) or my recent adventures in X3AP. ;)

Please do :) It's a genre (X3AP's) I can't wait to jump into myself - just need a proper joystick and an insultingly large monitor first.

I don't really bother to uninstall things.

Of course, I'm not running Windows anymore, so that helps free up a few terabytes.

The Witcher 3.

Some games stayed on my computer for a long time but then the day I tired of them arrived and I did not bother to reinstall when formatting or changing hard drives. Examples: Battlefield 2, Unreal Tournament 2004. Then there are games like Master of Orion 2: Battle at Antares which I tired of (last official version) and put aside until the first fan patch came out and fixed some of the annoyances whereafter I played it now and then and kept it installed and the new fan patch cements its place on my hard drives.

- Master of Orion (the first one)
- Master of Orion 2 (with a five year break ~2003-2008, see above)
- Cossacks, the anthology of the first games. My favourite is playing custom made maps.
- Mount & Blade (the first one) The combat really clicks with me. It lacks combos which is something I dislike.
- The X3 games seem to have come to stay on every hard disk I have.
- I know there is more on my desktop, that I cannot access now.

- Every Unreal game except Unreal 2.
- Serious Sam 1st, 2nd encounter and Serious Sam 3.
- Doom 1, 2 (not technically installed but I always have the WADS handy).
- Titan Quest

Since 1993 when I got my first PC:

- Prince of Persia
- Wolfenstein 3D

Pretty much since they were released:

- Duke Nukem 3D
- Quake, Quake II
- Diablo II

The others are not old enough to warrant the "long time" title by my standards.