I'm not a huge fan of Seven, but I think his most memorable quote is the last line of the original series: "Somewhere there's danger, somewhere there's injustice, and somewhere else the tea is getting cold. Come on, Ace, we've got work to do."
My fondness for Six comes from two things: A) I saw Colin Baker at a convention in 1986 and he was a wonderfully nice person; and 2) he was treated horribly by the show's producer, the script editor, and the powers that be at the BBC. Yes, overall the stories from his era are not up to standard (although "The Two Doctors" is splendid), but he only appeared in eleven stories! That's two less than Christopher Eccleston did! So it's not as though he was given much of a chance.
If you ever have the chance, please try and give his Big Finish audios a listen. The scripts are much better and he's much more mellow. And since you can't see his hideous coat, you won't be distracted.
i think sevens solioquy to an assasins to kill him point blank is quite memorable too because with that speech it cemented for me that yes this is somebody who can take down whole civilsations
i do actually know that baker was treated unfairly by the bbc and that he had his tenure cut short after the trial of a timelord he was unceremoniously shown the door and his last words on the show were carrot juice
and he may just have appeared in 11 stories he still appeared in more episodes then mr ecclescake ( who was the first doctor i watched btw )
and yes i am also aware fo hsi big finish audio's and i do plan to buy a few the real question is where to start though
I would recommend the Lost Stories. The scripts for the year that was lost to hiatus are now available as finished audio episodes. It's quite interesting to hear what that series would have been like had it not been lost. (Interestingly, they are also recording scripts for other Doctors that were never done for television. I'm quite interested in "The Foe from the Future" myself.)
On the other hand, if you'd prefer to start with the normal range, there is a list on Wikipedia of all the monthly releases, including which Doctor(s) feature(s) in them.
I see your point about Colin Baker appearing in more total eps than Eccleston, but since the modern show isn't serialized, I don't think one can think of a classic era episode in the same way you would a modern day episode. The classic eps are chapters in a story, whereas the modern eps are usually self-contained (except for the odd two- or three-parter), even when the series itself may constitute a larger story arc. My point is, Colin Baker didn't get a fair shot.