Ohhhhhh boy yes I've been into Warhammer since I was eleven. I didn't play or collect at all from age 18 until my thirties, but because I got back into painting minis because I was painting up Reaper, Heroforge and Wizzkids for my D&D games (I'm a Dungeon Master), I saw the new range of 40k, read about how much more streamlined 9th edition is compared to the previous versions and how the setting lore was actually moving forward and I was like "Oh hell yes."
So here are my armies. For now I have Space Marines and Necrons because it was easy to buy the starter set and build from there. I collect Sons of the Phoenix because I love the implied lore behind them (ie. that Cawl totally used leftover Emperor's Children geneseed to make them but told everyone, including them that they're totes Imperial Fists successors) and their regal colour scheme. The chapter badge is a pain though. I had to get custom transfer paper, hence not all the army has badges yet because they're so fiddly!
And so they have someone to fight, I have Szarekhan Necrons. I love the new lore for the Necrons. When I was a teen they were new and their whole deal was being emotionless husks puppeted by evil gods, but now they have actual personality and motivation. I still need to finish basing some of these... 
Once I have a thousand points of each of these, I'm probably going to switch to Adepta Sororitas (Yesssss space nuns!
) and Orks.