http://www.kotaku.com.au/2009/12/whats-with-all-the-war-video-games/
I have a feeling that the real reason is laziness.
Think about the work that goes into developing a fiction based FPS game, even something as simple and generic as Halo. You have to build the story with interesting protagonists and antagonists with plausible motivations, decide on and design a realistic setting, design cool weapons & vehicles that have interesting properties and far more.
Compare that to a real-war FPS’ development cycle: the 501st airbone with M1s & tommy guns vs evil satan nazis with MP40s at normandy. Okay thats the story, characters, equipment and location research done. Lets watch saving private ryan, calling it research if anyone complains and have cake.
Sometimes you can swap out the 501st for a generic ‘L0l, americanz iz teh heroez!!1′ squad, probably featuring a black soldier with an interest in rap, give it modern guns and make the enemy generic brown people or at least someone who speaks foreignese. Its still the same lazy shit.
On a side note, I see that bobby kotick is starting a new nefarious scheme to become the most hated man alive, wonder what this one will end up as. Maybe War Hero where you get weekly DLC featuring the real last moments of an actual soldier. If the Guild Of Calamitous Intent was real, he'd be on the council of 13

... and the lack of talent. It requires talent to design a game like Outcast for instance than designing for CoD or whatever. But you explained it already.

Or, you know, it could be because almost every single game was sci-fi or fantasy for 10-20 years of gaming, and people got fed up with that and wanted something different. And, in another few years, we'll go to something different (possibly zombies).
Reasons to go for modern(-ish) warfare:
Easy immersion. People can very easily see themselves in that role.
It is popular, so people are likely interested.
It is popular, so there are assets available on the market (if you buy your textures and the like).
There are lots of war movies on television and in theatres, and people might get in the mood for your game after watching Obi-Wan Kenobi with an m16.
If you do make something different, people will scream. Don't believe me? Look at Borderlands. It went from generic muddy "realistic" style to a colorful style. People went ballistic.
It is a lot easier to balance gameplay (since the guns are all going to be very similar).
Reasons to not go for modern(-ish) warfare:
Everyone else is.
Some stories can only be told with sci-fi or fantasy
Potential for different gameplay
And you complain that research for modern(-ish) warfare is just watching Private Ryan (awesome movie)? Okay. Research for sci-fi is watching Aliens and Starship Troopers. Research for fantasy is watching LotR.

I doubt laziness has anything to do with it. It takes plenty of work to make a GOOD war-game. You're right that an armed conflict in progress does provide ready-made parameters for game designers. That's all it really does, though. If anything, making a game based on historical events would be harder, because it actually does require some research into what the aforementioned parameters actually are. By contrast, most sci-fi/fantasy games can get away with eschewing research entirely by making stuff up.

And war games.
No. Not always. As for Borderlands, I have mostly read good comments about that game.

changes in graphics is one thing. for years we COULDN'T do anything realistic, so it was better to do sci-fi or something. then suddenly graphics could do something close to realism, so people jumped on the WW2->MW2 bandwagon.
Personally I think it's gone on a bit too long, but that's just me.
I'd imagine the current ongoing wars, fear of terrorism, and general love of boys (especially americans) for guns is another factor.

I would love to see Science Fiction games come back like Outwars and such. Nevertheless, I am currently enjoying the current modern era warfare games like World in Conflict or Operation Flashpoint I.
Anyway, it can't be as bad as the fact it seems all fantasy RPGs, to me at least, lately have been trying to be a LOTRs clone and such.

I personally don't think that's the reason.
That's more like it, imo.

I always immersed myself much better in military sci-fi games than in historical ones. Main reason is because all the WW2 shooters I ever tried sucked hard compared to the sci-fi ones. There's other reasons but the first one above is the one that keeps me away from historical games.
Modern warfare games, meh. COD4 and it's bastardly sequel are the shittiest modern warfare type games I have ever played and am glad I didn't buy them. The few that rule are rare and I while I can see there's a potential for them I haven't found any that are great since the new Operation Flashpoint got mainly bad reviews and I'm afraid to buy it.

Just like we have Sci-Fi and Fantasy games today :p. But, much like some people complain we don't have enough sci-fi, I am sure a lot of people complained that we didn't have enough modern-ish war games.
I am mostly referring to how they originally had a very muddy and "real" style. Then it became the hilarious ball of hilarity it is now, and a lot of people got really angry for some unknowable reason. It turned out okay, but a lot of people were still very vocal about how they didn't want the current art-style.

Absolutely.

War... war never changes.

I think you're grossly underestimating the difficulty of "making stuff up". It has to be internally consistent, immersive, realistic within the framework of the world it takes place in, and it has to work well in a game context. Trust me, "making stuff up" is a lot harder than it sounds.

To be perfectly honest, I'm almost sick of war games. Modern Warfare was a great change to the constant WW2 shooter, but now its getting a bit stale. Now even Medal of Honor is copying IW's move and is going to have a modern war game.
I've also noticed that the locations of war games is starting to get REALLY predictable. Ever since Battlefield 2, the desert has become the primary warzone. This has gotten to be extremely old for me, and is a reason I like the large pseudo-Russian areas of OFP and ARMA II - You don't see them that much. I've noticed that developers also seem to be getting tired of Iraq/Afghanistan, and with MW2 and the upcoming Max Payne 3 (Ugh), It seems that Brazil is the new war zone. Why? I have absolutely no idea.

Guys like war games, explosions and topless girls.