Alright. Are there any characters are good as kiritsugu in UBW?
Majority of Fate/Stay Night's characters are better written than Kiritsugu actually. That's because Kiritsugu was written by Fate/Stay Night's author and he didn't have time to develop him as much as FSN's characters.
Best written FSN character is Shirou, but only in the Visual Novel. Anime doesn't really do a good job on characterizing Shirou and cuts out too many stuff. Kirei is also plenty more complex in FSN's VN, mainly the Heaven's Feel route.
The visual novel in general has a lot more detail and characterization than the anime or Zero.
Are they as good as Fate/Zero and UBW? I like the servants aspect.
Mhm. They are all just as great as Fate. If you're going to go for Kara no Kyoukai's anime, I strongly recommend it. It was great and in terms of adaption, it's closer to the original source than Fate is. Although, movie 6 kind of alters things so it's easily the weakest out of the bunch because of it being a bad adaption of that particular chapter in the Light Novel. Still good tho'.
Kara no Kyoukai can be really confusing at first, but everything gets cleared up as the story goes on. Just pay a lot of attention.
Tsukihime doesn't have an anime adaption sadly. Except that old Tsukihime anime that is such a horrible adaption people pretend it does not exist, hence the ''Tsukihime anime does not exist'' meme.
Mahou Tsukai no Yoru adaption has been implied for the future though.