There was a distinct shift from role-playing to action with DF to MW, but DF beat MW hands down in the role-playing stakes, simply because there were (gasp) consequences to your decisions and skill-selection.
What was an excellent character-creation system was dumbed down to the eponimous 'birth signs'. Not that DF's system lacked faults, but it was a masterpiece compared to what MW offered. Same with many of the skills, sure -- the MW engine wouldn't support them (climbing in particular). But then you have to ask yourself why Bethesda went for an engine that wouldn't support the excellent spread of skills that DF had. Too cheap/lazy to develop their own? Incapable of doing so? Or just so contemptuous of their fan-base that they couldn't be arsed?
People laud the side quests in MW, but I found them every bit as crappy as the (almost) identical Fedex quests in DF. Go there, fetch this, come back, get your reward. At least DF had the advantage of not sending you to the same place, for the exact same thing, every time you played through.
But Ob is a whole new quantum leap in retardedness. From the ever decreasing number of skills, through the mind-numbing hand-holding, to the tedious and puerile dialogue. No levitation, no Nine Divines (in the very heartland of the religion for fuck's sake), a blatent disregard for their own lore, mammalian lizards with boobies, no thrown weapons despite the highly hyped Havok physics, no crossbows, fewer side quests -- all of which can be solved using Todd's Theorum of Role-Playing*, a MQ that is every bit as much linear as MW's or DF's (even though DF had the 6 possible endings that at least gave the illusion of variety), never-fail spell-casting and never-fail alchemy ('cause we know how frustrating it gets for little boys and Todd when they can't do something first time), missile-firing staves, LOTR wannabe elves.... shit, the list is endless and very, very fucking depressing.
So, DF was a masterpiece compared to MW. MW signalled the future of Bethesda games. MW was a bloody marvel in comparison to Ob. Ob is the light at the end of the tunnel we all knew was an oncoming train...
*Todd's Theorum of Role-Playing
Hit it with your blunt axe, whack it with a short/long sword/dagger type thingy, blow it to shit with a rocket-launch... er, I mean Staff, or snipe it with your super powerful, fully-Havoked, LOTR bow like the wee Legolas wannabe you really are... It's all fucking role-playing man!