If you could only choose one for each, what would you consider the greatest DC project of each decade on film or television? Here’s my list:
1940s: Superman (Fleischer Studios)
1950s: The Adventures of Superman (George Reeves)
1960s: Batman (Adam West)
1970s: Superman (Christopher Reeve)
1980s: Batman (Michael Keaton)
1990s: Batman: The Animated Series
2000s: The Brave and the Bold
2010s: Young Justice
I’d pick Justice League instead of The Brave and the Bold for the 2000s, but otherwise I’m totally on board with your list.
60’s: the Filmation shows and Adam West’s Batman
00’s: Justice League Unlimited, 2/3’s of The Dark Knight Trilogy and Superman Returns
Agreed on all other points.
I did say only one.
They’re ties 
Yeah, Hub, I really can’t argue with your picks (except for maybe the 2000s - there’s a LOT of competition there).
But if I were tasked to nominate challengers to put up against those #1 seeds?
1940s: Superman Serial
1950s: Blackhawk Serial
1960s: Filmation Cartoons (all of them!)
1970s: Super Friends
1980s: Superman II
1990s: Lois & Clark (TV Series)
2000s: Justice League (DCAU Series)
2010s: Wonder Woman (DCEU Film)
2020s: The Green Lantern Corps (DCEU Film)
Actually, The Adventures of Captain Marvel Serial might be a better competitor than the Superman Serial for the 40s.
(But neither beats those Fleisher shorts!)
As an aside, CBR ran a bracket-themed competition back in March while we were doing Meta Madness, but theirs was filled with 64 animated series: DC, Marvel and independent.
Even though they were up against some heavy Marvel competition, DC swept into the Final Four with Justice League, Justice League Unlimited, Young Justice and Batman: The Animated Series. BTAS won it all. 
I REALLY wanted to say the Lynda Carter “Wonder Woman” TV show for the ‘70s, but the first Christopher Reeve “Superman” movie is definitely the top pick for that.
I’d probably go with Nolan’s “Batman Begins” & “The Dark Knight” for the 2000’s, although the “Justice League” animated series is a strong contender for that as well.
2010s: YJ
2000s: TDK
1990s: BTAS
1980s: The Batman
1970s: Super Friends
1960s: The Adam West Batman, forgot its name
I don’t really know much before this moment
I consider ‘greatest DC project’ to include series/universes. If ‘project’ is limited to a specific TV series or movie, then the first to launch the universe can be held responsible for the greatness.
1940s Superman cartoon
1950s ??? (probably Superman, but I’ve never seen it)
1960s Batman (Adam West)
1970s Superman The Movie
1980s Batman
1990s DCAU
2000s Nolanverse
2010s Arrowverse