Dominion and Neuroshima Hex. Take combat from Neuroshima and long term strategy from Dominion.
Also, Lesbian Spider-Queens of Mars with Space Phallus.
Borderlands 2 and... Maybe Metal Gear Solid 3. Something with jungles, stealth, survival and camouflage. Imagine that with multiple player classes, skill trees, millions of weapons (with rarity levels) and so on. I think it could work.
XCOM and Mass Effect.
Everything from the former, characters from the latter. Replace the aliens with reaper-types and we're set.
Syndicate's world, with GTA's gameplay.
Just cause 2, battlefield 1942 and rollcage.
Crusader Kings and Sins of a Solar Empire. Basically I just want CK2 in space though.
Neither are for PC (yet, I still have hope) but Red Dead Redemption and Way of the Samurai.
Grand Theft Auto and Mass Effect.
= Space Adventure without being chained to your Pilot Seat
Mount & Blade (3d Combat)
Incursion HotgK (Gameplay Mechanics)
= Skyrim Killer
Space Station 13
any decent 3D Shooter Engine
= progressive Take on immersive MORPG/MUSH
Arma 3 + Space Rangers
I am very boring and conservative compared to the grander imaginations on display above, but give me an ARPG that combines the driving sense of purpose that comes from Din's Curse with the flash and polish of Diablo 3. I could be playing that for a very long time.
Baldur's Gate/2 with IWD2. The original Bhaalspawn saga in beautiful, beautiful 3.5E. There was actually a fan project to do that but it got dropped.
Metro 2033 with STALKER. I am thinking keep the game in the metro, but make it mostly freeroam. Would be awesome and realistically quite doable, I think between Metro 2033 and 2034 they have enough tunnels to connect most major stations already.
Dark Messiah of Might and Magic + Skyrim= huge open world with dynamic and fun fighting system
Witcher 2 X Tekken Force
Why don't modern games have gameplay based on skill and timing anymore?
Shift 2 + Football Manager
Paint your cars daft colours and then watch a crappy replay of the highlights of the race!
Er, no, other way around, manage your cars, cash, team, upgrades and race scheduling and then take to the track and crash into things.
Freespace 2xDarius Gaiden
My kingdom for an aquatic space combat sim.
I'd love an Elder Scrolls game with the detail and sneaking of a Thief game, or even Deus Ex or Dishonored. Basically, much more detailed cities.