For me they would be;
1. Spider Man
2. X-Men
3. Guardians of the Galaxy
I've been a Spider Man fan since the 90's (I'm not someone who ever uses the term fan to describe myself because...well a lot fanbases are toxic nowadays) however I'm a total nut for anything Spider Man-related. I got my start in the 90s with the Clone Saga and the Animated Series, collected the comics and toys back then grew up a bit and became "too cool" for it so to speak, recently as of this time last year I went on a very expensive nostalgia spree and purchased Spider Man trades, toys, etc.
X-Men I've loved since the 90's as well, the Saturday morning cartoon (which ran on the now defunct Fox Kids iirc) is what got into the X-Men mythos. I had a very modest collection of X-Men figures from the 90s (I think mainly Sauron and a variation of the dozen or so Wolverine toys that were popular at the time). The early 2000s movies also revamped my interest in the X-Men, as of 2017 I've been collecting X-Men figures as well and have the whole Warlock wave and most of the Juggernaut wave of legends figures.
Guardians of the Galaxy, I will admit that my enjoyment of the films is what influenced me to branch out further into GOTG beyond the movies; reading the comics and learning about the original team of GOTG and the differences and origins of the current comic heroes versus the MCU versions.