I have been pondering the amount of material on each Doctor available in the Whoniverse, considering TV, audio and novels/novellas (I'm not quite sure how to tabulate comics and short story collections).
Time on TV
This is uncontroversial. The order is:
This is counting screen time as the Doctor. There have been more individual Tenth Doctor televised stories than for any other except Four, but most of them are only a single 50-minute episode, so in screen time he is still behind Two, though I think now comfortably ahead of Five.
It is a tight squeeze at the top, but Eight just beats Seven - there are 73 Eighth Doctor Adventures, and he features as lead or joint lead also in 2 Past Doctor Adventures and 3 Telos novellas. That is a total of 78, just ahead of Seven's total of 76 (61 Virgin New Adventures, 1 Missing Adventure, 12 Past Doctor Adventures, and 2 Telos novellas).
There are now 30 New Series Adventures, 12 Decide Your Destiny books, 10 Darksmith Legacy books, and 5 Quick Read novellas featuring the Tenth Doctor, which makes a total of 57. I doubt if he will catch the leaders now.
Four and Six
For Four I count 8 Virgin Missing Adventures, 12 Past Doctor Adventures, and 1 Telos novella; I am not counting the novelization of Doctor Who and The Pescatons. For Six I count the three 3 Target Missing Episodes, 5 Virgin Missing Adventures, 11 Past Doctor Adventures, 1 Telos novella, and the charity production Time’s Champion; but I am not counting the novelization of Slipback. In both cases that is 21 books with Four or Six as lead or co-lead.
Actually all four of these are pretty close. For One I count 5 Missing Adventures, 8 Past Doctor Adventures, 2 Telos novellas, the scripts of The Masters of Luxor and Farewell Great Macedon and a half point for Jim Mortimore's Campaign, for 17½. For Three I count 5 Missing Adventures, 11 Past Doctor Adventures, and 1 Telos novella but not the novelizations of the radio plays, which makes 17. For Two, there are 4 Virgin Missing Adventures, 10 Past Doctor Adventures, and 2 Telos novellas; and for Five there are 5 Virgin Missing Adventures, 10 Past Doctor Adventures, and 1 Telos novella, which is 16 each. I bump Five ahead of Two on the basis that a Missing Adventure beats a Telos novella.
There are 6 Ninth Doctor books and I doubt if there will be any more.
He may be bottom of the pack for TV time but beats the others in terms of audios as well as books, thanks to Big Finish treating him as the incumbent Doctor for much of the 2001-2005 period, and then the BBC7 series.
Presumably this ranking reflects simple availability of the lead actors to do the Big Finish plays.
This is very tight and subject to change. I am crediting Three for 7 Companion Chronicles, The Ghosts of N-Space and The Paradise of Death, and also for the not-yet-complete The Three Companions, which makes sort-of 10 stories in total; while Four has The Pescatons, Exploration Earth, the first two parts of The Hornets' Nest and 5 Companion Chronicles, making 9. But this will look different in a few months.
Ten and One
Again this is very tight. All three of them have five complete audio stories - 5 Companion Chronicles for One and Two, and 5 audio-only novels for Ten. I put Two ahead though because he also features in the ongoing The Three Companions, which gives him a sixth.
Poor old Nine has no audios out at all. Aggregating
For what it's worth, averaging out the rankings you get the following:
Four - Top on screen time, decent number of books, let down by his audios but is improving there
Eight - just tops books and audios, but way way behind on screen time.
Seven - strong competitor on audios and books, let down by screen time
Six - likewise
Three - decent mid-list on books and audios, pulled up slightly by screen time
One - tie with Ten broken by having more screen time though fewer books and same audios
Ten - now unlikely to rise higher, unless he starts doing audios
Five - surprised to see him this low, but only scores well on audios
Two - despite good screen time, has not been the most popular subject of spinoff fiction
Nine - poor chap, least books, no audios, and second shortest screen time