I wouldn't want a serious relationship with any of them. (maybe the master. but that's got a guaranteed time limit, so it's not the same.)
but if I had to pick a fling with somebody? it would be jack.

no mere human can get past the time lord angst.
I wouldn't even try.
I'd just hit on some hot aliens and get tagged as "that miserable space slut" by angry viewers and then I'd die violently. GOOD TIMES.