OK, everyone knows the Bach 48 but, since he wrote them, there appears to have been few others who attempted a set of P&Fs in all the keys (various definitions, therefore various numbers). Indeed, Bach wrote his in 1722-42, then nothing, then Klengel (pretty obscure - he was a pupil of Clementi) wrote a set of Canons & Fugues in 1854. Then nothing.
Then, since the 1940s, it seems increasingly that everyone is at it!!
Here's the list I have below. Does anyone know any more?
Complete Sets of Preludes and Fugues in All Diatonic Keys
Bach, J. S. (1685-1750) Well-Tempered Clavier, Vol. I Well-Tempered Clavier, Vol. II 1722 1738-1742
Bell, Larry (b. 1952) 12 Preludes and Fugues, Reminiscences and Reflections 1993-1998
Bellak, Richard C. (b. 1945) Fugal Dreams: Jazz Preludes and Fugues for Piano, 12 1977, 1985
Bentzon, Niels Viggo (1919-2000) Det tempererede clavier: 13 volumes, each with 24 Preludes and Fugues 1964-1996
Diamond, David (1915-2005) Preludes and Fugues, 52 1939-1940
Gál, Hans (1890-1987) 24 Preludes, 24 Fugues 1960, 1980
Hindemith, Paul (1895-1963) Ludus Tonalis 1942
Huber, Hans (1852-1921) Preludes and Fugues for four hands, 12 1890
Johnson, David (b. 1942) Preludes and Fugues, 12 1995
Kapustin, Nikolai (b. 1937) 24 Preludes and Fugues 1997
Klengel, A. A. (1783-1852) 120 Canons and Fugues 1854
Madsen, Trygve (b. 1940) 24 Preludes and Fugues 1996
Martin, Henry (b. 1950) 24 Preludes & Fugues 1990-200
Novák (Zemek), Pavel (b. 1957) Preludes and Fugues, 24 1990
Reizenstein, Franz (1911-1968) Preludes and Fugues, 12 1955
Shchedrin, Rodion (b. 1932) Preludes and Fugues, 24 1964-1970
Shostakovich, Dmitri (1906-1975) Twenty-Four Preludes and Fugues 1950-1951
Slonimsky, Sergey M. (b. 1932) Preludes and Fugues, 24 1995