The Sideshow portraits are actually very well executed. As seen in examples above, some tweaking (repainting at the very least) can show them off to their best advantage. Great job JustinLuck, dekadentdave, and Customikey.
As for the best Han Solo sculpts that I've seen, the distinction has to go to the great Arnie Kim. It's not just about accurately capturing Harrison Ford's likeness. It's about capturing Solo's crafty smirk and the arrogance with which he carries carries himself. Mr. Kim achieved all that with great subtlety:
Here's another Solo portrait by Mr. Kim. Here, Solo displays that look of incredulity his countenance takes on when things aren't going quite right:
These sculpts are all very nice but none of them including SSC's screams Harrison Ford to me. Even the 1/4 I felt was lacking. I have yet to see a HF headsculpt that really captures the character for me in either Han Solo or Indiana Jones.