The first three Star Wars films (episodes IV, V, and VI) are basically the Luke Skywalker show. Han Solo and Leia Organa vie for the #2 spot in the rest of the original trilogy. You can see a complete breakdown of relative screen times, both in percentages and scene durations, thanks to the work of redditor /u/--TheForce--, who shares the results of his work on Data Is Beautiful.
In 13 charts, he addresses all of the Star Wars films, as well as the film series within the franchise. No character is on all of the charts, although C-3PO and R2-D2 come close.
-via Born in Space