I think a lot of you are not understanding what gameplay is.
Its not the items or the story or the atmosphere or the stats system. Its how it controls and feels. If you just took quake3, deus ex and system shock quake3 comes out on top with gameplay. Even quake1 does. You might enjoy having stats and stuff and that might even make the game for you… But thats not the gameplay.
Another example would be comparing the superb Dominions3 to Warcraft2. I much prefer dominions3 but warcraft2 has the better gameplay.
So with dark messiah you have gameplay that rivals any FPS. Its a better use of Source engine than even halflife2 in terms of gameplay. Then if you compare the melee action in Dark Messiah to ANY other RPG its miles ahead. Morrowind, 1 swing. Oblivion, 4 swings. Darkmessiah, 4 swings, 4 fatalities a weapon, backstabs, knife throws, kicks, knockdowns, leap attacks, disarming attacks, etc…
So when i say Arkane+bethsoft+id = best RPG ever its because it will have the gameplay of dark messiah with the better questing, exploration, etc of oblivion.