I dont know what is misssing in other scales, but in 1/48:
MiG-23
Im working on a Kazan set right now, and it still lacks a lot to make a great looking plane without own surgery.
MiG-17 F and PF
the only kits I have seen are Hobbycraft and Smer. I know what Hobbycraft has done, and this is not the awnser, the Smer kits feels like blown up 1/72 kits.
MiG-29
by Hasegawa or Tamyia
SU-7 and maybe SU-11
the OEZ kit is well... it might look good when you spend 50-60$ on eduard updates, but bare ? no way.
SU-20
It might not have been a great airplane, but it certainly looks better than bo