I think we all have similar experiences.
For me, I started by trying to preserve what I had as a younger person. I still had my 2600 and games, but I was more concerned with my Atari 8-bit collection. Most of the games I had were on disk, and I knew they wouldn't last forever. So I started buying cartridge versions of games, and really got into emulation as a way to preserve what I thought would eventually no longer be viable.
Once middle age set in, and my kids were a little older, I found out I had a little extra income that I could play with, and I decided to try out all the systems I drooled over as a kid, but could never afford. 5200, Colecovision, C64, Vectrex, etc. And also, buying whatever 2600 games I could find that I never had before. My kids were really into Nintendo in this period, so we also started buying those systems and games. NES, SNES, Genesis, etc. My kids loved that stuff, and I found that I did too.
Over time, the hobby has gotten much bigger and much more expensive. At this time, I like to fix old systems that are broken, or update them to work on modern TV's. Buying is no longer so important to me. I have tons of games that I will play and enjoy for a long time.