Ended up going down a maiden-F1GP-victory rabbit hole after a question posted on the Midweek Motorsport Listeners' Collective.
Maiden GP winners per decade:
(Figures in brackets include Indy 500)
1950s: 15 (24)
1960s: 17 (18)
1970s: 22
1980s: 14
1990s: 10
2000s: 14
2010s: 5 so far
Track with most maiden GP winners: Monaco (9 - Fangio, Trintignant, Brabham, Hulme, Beltoise, Depailler, Patrese, Panis, Trulli). Indy 500 has 10.
Longest gap between maiden victories:
Alessandro Nannini, 1989 Japanese GP -> Michael Schumacher, 1992 Belgian GP: 2 years 10 months 8 days
Mark Webber, 2009 German GP -> Nico Rosberg, 2012 Chinese GP: 2 years 9 months 3 days
Michele Alboreto, 1982 Caesars Palace GP -> Ayrton Senna, 1985 Portuguese GP: 2 years 6 months 26 days
Current streak come Sunday's Hungarian GP: 2 years 3 months 5 days since Valtteri Bottas won the 2017 Russian GP. The Nannini/Schumacher record will remain if we get a maiden victor this season.
Most maiden GP victories in a season: 1982 (5 - Patrese, Tambay, de Angelis, Keke Rosberg, Alboreto)