I've been into collecting since 1996 and I started by targeting what I grew up with - 2600, INTV and CV - and what I still had in my possession - NES, Atari 2600, TI 994/a.
What started as a small nostalgia trip turned into a full-blown hobby that is very enjoyable! I lost a few years (2003-2005) due to divorce and more recently for a family illness. I'm no longer actively collecting since I've found that even my "play" money needs to be for the family first at this point in my life so my collections have shrunk and ground down to a near standstill.
At the height of my collection - around 2001 - I had an entire gaming apartment set up with roughly 25 systems across 2 rooms(double parlor), a computer network in a 3rd(1st bedroom), a ton of board games(kitchen) and a small room set up with a library(2nd bedroom). I gotta have my books. I also helped plan a couple of the old PhillyClassic conventions under David and Chuck. Had some good times with this hobby and the great people in it!
Now I've moved into my own house(finally!) with my fiancee. I have the space for collecting but I have found I like having small, multicart and emulation collections so I doubt I will ever have another massive physical collection again. I've settled into multicarts like the Harmony, LTO Flash and Krikzz Everdrive carts. One cart, one system, real hardware. I also have an X-Arcade Cabinet for all my emulation and party hosting needs. I've had it since 2012 and it still gets used 2-3 times a week by myself and guests of the family.
These days it's just about playing the games and enjoying life.