When film emulsions were the only method of recording a scene or object/person, there was a clear division of labour. The 35 mm film and camera was selected when convenience, speed and low cost were important. The small negative had its limitations when the utmost in image quality was required. Then the medium format camera could be selected. Less easy to use, more costly and the maximum of 12 images was a limit. Fashion photographers had assistants that were involved in loading cassettes for the master. Commercial photographers and art photographers (zone system required) used field and studio camera that could be loaded with one negative at a time. Speed was replaced by contemplation. Large negatives were costly and careful processing was needed to make the most of it.
Kodak tried to make the 35 mm camera a challenge for the medium format camera by introducing the Kodak Technical Pan film. Incredible resolution, but extremely slow speed: the best results require an EI of 16 ISO (incidentally the speed of the original Pan-X).
My own testing shows that modern film emulsions are the equal of 35 mm sized sensors, when you take care of all variables. This is of course not the current style of photography. Modern consumers require ease of use, foolproof processing and fuss-less sharing of images.
A film that can surpass even a 50 Mp sensor in 35 mm size is the Belgium-Agfa made microfilm, that is sold in several guises. The Adox version is well known as is the Spur DSX. The bad point about these films is the very low speed: more than ISO 12 is not advisable when one wishes to get good shadow detail according to the rules of the zone system. If you have scenes without deep shadows ISO 25 is possible. Spur has recently introduced a new developer for this film, the DSX 200. With this developer a realistic speed of ISO 100 and even ISO 200 should be feasible. I will test the claim soon. If true this is a major boost for quality conscious Leica photographers. The Apo-Summicron range (50-75-90) could be exploited to the full.
When Amaloco was a household name for photographers, the AM74 was a favorite developer because it could be used with all kinds of film and produce outstanding sharpness. Grain was a problem but when printing at a maximum of 10 times enlargement, everything was fine. An improved version of this film is now on the market as Rollei Supergrain with (claimed) much improved performance.
The last new developer is the Spur Speed-Major, a push developer without the usual loss of shadow details. This developer allows the HP5 to be used at EI 2000 without loss of shadow detail and without a substantial grain increase. When true (test will follow soon) analog photographers can now move into really high-speed photography (above 3200 ISO).