Of the girls listed, I liked Penny the best, but I will admit to being a little biased that way, having made Jimmy propose to her in the S6 finale...
A very close second was the unknown red-head from SM; always thought the series should have done more with her. As it was, the whole soul mate thing was ignored if your name wasn't Kent...
Angela from SG was cute, so I could have lived with her as Jimmy's girl -- and, of course, there's Lucy. The long-time comics reader in me always wanted Jimmy to finally get Lucy in much the same way that I wanted Clark to get Lois, or Lois to get Superman: after all the stuff that the former had to put up with from the latter in each case, they
deserved to get the girl (or boy) if they still wanted her or him! Not sure that the object of their desire deserved the seeker, so to speak, but that's a topic for another time, and probably another forum.
And I remember the Jimmy-marries-Linda story, too: classic Weisinger SA stuff, and fairly well handled, though the resolution of the soap-style plot always seemed a bit off, especially by comparison to Lois' reaction to learning Clark's secret in the series. But those were simpler days...
Phil