This would be hard for me to answer because I love almost all of Paul's original studio albums (with the only exceptions being McCartney 2 and Pipes of Peace), and as a result I tend to just kind of rotate through them all pretty evenly. I guess I'd say:
Most
1. Egypt Station. This is one of my very favorites, lots of variety and I like every single song on it.
2. Ram. Love it, lots of fun to listen to and it rocks. The only thing I think it's missing is a great closer, as I don't like Back Seat of My Car much.
3. Tug of War. I think every song is fantastic, with the glaring exceptions of What's That You're Doing and Ebony and Ivory.
4. New. I really enjoy this one especially Early Days and Hosanna. It has a different, more "slick" feel than the other albums, but if I'm in the mood for that it's great.
5. McCartney. I love the feel of this album. Oo You is an underrated gem. I like everything except Teddy Boy and Kreen Akrore.
Least
(The real answers here would be Run Devil Run, Kisses on the Bottom, the Russian album, and Give My Regards to Broad Street, but I think you're asking about Paul's original albums)
1. Pipes of Peace. To me, this one is just bland all the way through, so I don't play it as much as the others.
2. McCartney 2. The opposite of POP, I love half of M2, but dislike the other half, so it's very up and down, with too much down. It's like a half of an album, so I end up playing it less. Front Parlor, Frozen Jap and Bogey Music are the ones I really dislike.
3. Press to Play: I like this album and think it's generally underrated, but I just don't get around to listening to it very much. I love Good Times Coming/Feel the Sun, and dislike Talk More Talk and Pretty Little Head.
4. Off the Ground. I like this one a lot, except for Looking for Changes and Biker Like an Icon. Hope of Deliverance is way overrated too, not sure what people see in that one. I absolutely love the ending with Wine Dark Open Sea, C'mon People, and Cosmically Conscious. I suppose this gets played slightly less than some others.
5. Flowers in Dirt. I feel guilty listing this one as I do love the majority of the album. I can't listen to Put It There without starting to tear up. But You Want Her Too and Ou est le Soleil are among my least favorite songs Paul's ever done, and the overall production is too 80's sounding, so I get to it a little less.