It's because Epic turned their backs against the people who made them great. UT99 was a major hit back then. Then all they do is make a updated version in 03,04 and UT3. Since those weren't selling so good, they blamed piracy. Then go create a whole new IP for consoles (Gears of War) and say we love console players now. At least thats my opnion.:\
It's not merely that Epic turned its backs on PC gamers. The ire aimed at Epic is also the result of what they did to the Unreal Tournament series.
For those of you who are unfamiliar with it, the original Unreal Tournament, released in 1999 (aka UT99), was the greatest online multiplayer FPS of all time. It felt more like an athletic cybersport than a disposable game. It had legions of fans, numerous server-based communities, hundreds of clans, and there must have been over 10,000 custom maps and mods made for it.
Then Epic released UT 2003 which changed the movement style and the weapons and added an announcer voice (that supposedly sounded really ghey) and people hated it. They improved upon it a bit with UT 2004 which is a good game in its own right for the vehicles-based Onslaught game and the Invasion-RPG mod.
Where Epic really screwed up was with UT3. UT3 was released on both the PC and consoles. The feel of the UT3 game play itself wasn't too bad, but everything surrounding it was god-awful. Upon release it seemed like a buggy beta and the server browser barely functioned. It was also heavily consolized, having a horrific user interface and lacking a great many of the user interface features and build quality that UT players had taken for granted. As a result, UT3 totally failed compared to the previous games and never had decent online player counts. it was a stillborn abortion. It also had dark, grungy, Gear of Warrified looks that people didn't like. UT fans felt like they'd been sold out to the consoles.
If Epic is to redeem itself, then they need to produce a first-rate, highly polished UT99-2.