Well... I would say either Fable or Dragon's Dogma. Why? Because while Fable is fairly tale, Witcher is more folklore based. Heavily. With quite the slavic feel in it (which isn't suprising, considering where the universe of the game was created) - althought it's medieval, it's not so 'knightly'. The royalty are snob assholes, and the peasants are being 'smart', gaining where there can, how they can. Another important, in my opinion, part of the atmosphere is that it ain't shiny. Like I metioned - you will have to deal not only with literal, not sentient monsters, but also with people who deserve to die even more than they do. The whole universe is bitter grey - you try to do something good only to learn you either helped someone bad or you were just been used. I think it's great, but it's my opion, again. :)
And, of course, the whole game is not only dark mood - there is also many happy or just joyfull parts, even relaxing, like Chapter 4. See it for yourself.
Mechanically combat is, mostly, stat based. As in - D&D styled, almost. For example - later on, when you have high enough dexterity you won't get hit and can 'tank' enemies you, earlier, lured to fight one-on-one. Thus - there is no such thing as your 'opening', because attacking doesn't stop enemy, usually, from attacking, unless it's said one-on-one and enemy can be stun-locked. The dificulty is more of a knowledge - to know what attack with what (which style), when and with what potions - especially if you play on higher diffs.
Tekkaman-James: Some features, such as the ability to have...relations...with various characters seems a little forced and not very well designed.
This is one of the jolly parts. The game is based on book series and there, too, 'casual' sex was something normal. So you hitting on
many woman in game isn't strange, 'lore wise', but it's still your choice. It doesn't really change anything in game. But yes, they went with more mature way with relationships in W2 and 3.
EDIT:
Two things I forgot to mention:
1) Choices
do affect the future. Usually after some time, so you have to 'live' with consequences of your decissions.
2) There is no real need to grind in this game, because there are only few spots worth it, and ironically - there are filled with powerful monsters. Instead, you can just do other quests and/or prepare specific potions and oils to help you with a difficult enemy.
Wait until W2, if you plan to play 'Dark Mode' to complain about grinding, belive me. ;P