The thing with Patrick Stewart was that he made you take notice when he spoke. He had audiences hanging on his every word and left you enthralled. Sure, we saw him be funny as was the case in his collaborations with his friend Seth MacFarlane, but he made you listen and left you mesmerized. I know I'll be crying like a baby when I see his (potential) last performance in the theater in December.
And as with many great actors who we've lost, a rewatch of Stewart's best performances is highly recommended. Ice and Money already nailed down Captain Jean-Luc Picard in the "Star Trek" franchise, Professor Charles Xavier in the "X-Men" franchise and Avery Bullock on "American Dad!". I'm going to add on King Claudius on "BBC Television Shakespeare", Lord Yupa in the Disney English dub of "Nausicaä of the Valley of the Wind", King Richard in "Robin Hood: Men in Tights", Captain Ahab on "Moby Dick", Ebenezer Scrooge in "A Christmas Carol", himself on "Extras" and Darcy in "Green Room".