Yes.
And, believe it or not, that is the most sensible answer you will get.
Why do you ask? Which do you own? If neither, then get KotOR I; not because it is better, but because it it is a seminal RPG and there wouldn't
be a II without it. And then you'll
know whether or not you want KotOR II and you won't need to ask us.
The story lines are
different; better is only personal opinion and mine might not agree with yours. NPC sidequests and romances might not float your boat; they don't float mine and they always felt tacked on (at least the sidequests in NWN yielded some benefit) and the romances juvenile.
Personal opinion? Kotor II is better. Yes, it has it's problems and it appears to have been abandoned by LucasArts now, but it is a very playable game once you find your way around it's faults.
The story line is darker and more intelligent, the characters and influence scheme (limited as it is) makes the DS path more believable, and upgrades actually make a difference now, and to more than just lightsabers.
II has been the recipient of more interest from the modding community. There are a great deal of substantial mods for II, including the USM, High level force powers and more (go
here for more details). Everyone who liked the game is waiting for the TSL Restoration Project to put back the content that unfairly hit the cutting room floor (go
here for details). Others are even putting the droid planet, M4-78, back (go
here for details).
The clincher for me is that I have now played II more than I. And now that I have the USM mod I have played it twice more.
Well worth a place in anyone's collection (and it hasn't been a bumper year for RPGs).