http://thetimescales.com/Doctor_Who/...php?seriesid=1

This website offers readers the chance to rank each Big Finish play, and above is the link to their Top 175. It's not exactly definitive - some stories only have 20 odd votes - but it is interesting.

Top 10:
(1) 140. A Death in the Family
9.6/10 (43 ratings)
(2) 40. Jubilee
9.1/10 (48 ratings)
(3) 81. The Kingmaker
9.1/10 (40 ratings)
(4) 48. Davros
9.1/10 (46 ratings)
(5) 14. The Holy Terror
9/10 (50 ratings)
(6) 29. The Chimes of Midnight
9/10 (63 ratings)
(7) 43. Doctor Who and The Pirates
8.9/10 (36 ratings)
(8) 34. Spare Parts
8.9/10 (56 ratings)
(9) 120. The Magic Mousetrap
8.9/10 (42 ratings)
(10) 115d. The Word Lord
8.8/10 (38 ratings)
Bottom 10:

(165) 70. Unregenerate!
5.7/10 (30 ratings)
(166) *Cryptobiosis
5.6/10 (21 ratings)
(167) 67. Dreamtime
5.6/10 (29 ratings)
(168) 55. The Twilight Kingdom
5.5/10 (26 ratings)
(169) 106. The Dark Husband
5.5/10 (30 ratings)
(170) 42. The Dark Flame
5.3/10 (26 ratings)
(171) 36. The Rapture
5.1/10 (30 ratings)
(172) 78. Pier Pressure
4.6/10 (24 ratings)
(173) 53. The Creed of the Kromon
4.6/10 (29 ratings)
(174) 41. Nekromanteia
4.3/10 (26 ratings)
(175) 75. Scaredy Cat
3.8/10 (26 ratings)
Do we agree with the site's users' rankings? I quite liked "Scaredy Cat"!

Si.