Coming late onto this thread as usual:
Mikhail Alexandrovich (more he-man-looking than Dimitri)
Boris and Andrei Vladimirovich were both good-looking before dissipation caught up with them.
You can see that I'm a sucker for uniforms and moustaches, but I don't like mutton-chop whiskers at all, so that excludes Alexander II, along with Konstantin Konstantinovich and Sergei Alexandrovich before they moved on to full beards.
As far as connections are concerned, Felix Yussupov Senior was better looking than either of his sons, and can I put forward Nikolai Koulikovsky, whose two sons were also good-looking.
Of non-Russian princes, my pin-up boy must be Ernst August, Duke of Brunswick. I agree that Heinrich of Prussia was very good-looking, though I'm not mad about beards. There is also Louis of Battenberg, and Alexander of Teck (who remained distinguished-looking even after losing his hair).
Ann