BO1 regularly wins on polls like this when vote counts are high.
As someone that started with WaW, I really liked BO3, but I actually think BO1 is my favorite. I felt like it was an extension of everything that made WaW zombies so much fun, the map variety was great, and most importantly it was beginner friendly with a very high ceiling for skilled players.
In BO3 there really wasn’t much you could do with beginner players, the game became so complex that it was hard to play with noobs.
Also, I feel like it is extremely overlooked on Reddit and by Zombies YouTubers how much gobblegums killed public lobbies. I know those two communities only focus on solo play, but 4 player zombies was absolutely incredible in WaW and BO1, not just with friends, but public lobbies were also fun, and gobblegums killed a lot of that.