So I just recently discovered that WMF is now publishing stats for media files.
So in terms of most popular videos, it seems to be mostly space and porn. (This list is url of file minus the https://upload.wikimedia.org part then a comma, then the number of downloads on 2015-07-25)
/wikipedia/commons/9/92/Cynopterus_sphinx_fellatio_no_music.ogg,58270 /wikipedia/commons/c/cc/Andromeda_and_Milky_Way_collision.ogg,2036 /wikipedia/commons/f/fa/Ejaculation_Educational_Demonstration.OGG,1819 /wikipedia/commons/4/4b/Erection_development_animated.ogv,1035 /wikipedia/commons/e/e0/A_handjob_video.ogv,981 /wikipedia/commons/7/73/Male_masturbation_followed_by_ejaculation.ogv,928 /wikipedia/commons/6/64/Agenor_fait_un_levage.ogv,811 /wikipedia/commons/9/94/Debbie_Does_Dallas.ogg,750 /wikipedia/commons/4/4f/Tourette's_tic_long_medium_192kbps.OGG,740 /wikipedia/commons/c/c5/Spontaneous-Ejaculation-in-a-Wild-Indo-Pacific-Bottlenose-Dolphin-(Tursiops-aduncus)-pone.0072879.s001.ogv,648 /wikipedia/commons/3/31/L'heure_du_th%C3%A9.ogv,634 /wikipedia/commons/3/31/Ziteil%2C_aerial_video_with_interior_view.webm,617 /wikipedia/commons/e/ef/Speedsolving_a_3%C3%973%C3%973_Rubik's_Cube_with_Fridrich_Method.ogg,602 /wikipedia/commons/3/3a/Condom_placement_demonstration.ogv,582 /wikipedia/commons/1/12/Hypospadias_penis_masturbation.webm,578 /wikipedia/commons/5/58/Ap17-ascent.ogg,566 /wikipedia/commons/3/3e/Massages.ogv,510 /wikipedia/commons/8/83/Elephants_Dream_(high_quality).ogv,496 /wikipedia/commons/c/c3/Miss_Butterfly.ogv,496 /wikipedia/commons/3/3d/Simulaci%C3%B3n_Tsunami.ogv,480 /wikipedia/commons/6/67/Pentagon_Security_Camera_1.ogv,476 /wikipedia/commons/0/0e/Jupiter_from_Voyager_1_PIA02855_thumbnail_300px_max_quality.ogv,466 /wikipedia/commons/9/94/A11v_1092338.ogg,446 /wikipedia/commons/c/cb/A_male_masturbating_with_lubricant.ogv,427 /wikipedia/commons/b/bc/Female-masturbation-electric-massager.ogv,418
See more at https://dpaste.de/Yuym
This comes from the top1000 csv zip files at http://dumps.wikimedia.org/other/mediacounts/daily/2015/, using the mediacounts.2015-07-25.v00.sorted_key17.csv file.
Anyways, thought it would be interesting to this list.
-- Brian