Back in 84 around my birthday Go Bots came out. My mom showed me them in the flyer and asked me if I wanted some for my birthday and I was all over it. Vehicles, robots, what couldn't I like?
Towards the end of that school year Transformers (G1) came out which were automatically cooler. They generally were bigger and had better looking vehicles and transformations. Starscream was the first one I got.
The last G1 figure I picked up was flattop, and I was really too old for toys at that point.
Then there was a break. I used to sometimes check out G2 stuff at the store, but I didn't have money to "waste" on toys at the time.
I came back for Beast Wars and got totally into the show and started getting some of those figures (when I was in University). I had some Beast Machines figures, which I liked ok...
Then a longer break. I would pick up the odd RID figure (Megatron, combaticons), but I didn't like the cartoon. I got Armada Starscream, but wasn't too into Armada overall.
It wasn't until Unicron came out that I really came back. I wanted a Unicron figure since I was a kid and when I saw they were making a figure of him for Armada I had to have it. At the time I thought it was a lot for a figure, little would I realize how easily I spend money on the figures now and Unicron is nowhere near the most I've paid for things.
Energon was cool and had lots of hommages (Galvatron, Shockblast) to keep me interested and the TRU reissues were cool (if kind of expensive). At that point I had dug out all of my old stuff and started cleaning Spawn, wrestling and Turtle figures away to make lots of room for Transformers.
I've been buying practically everything since Cybertron. There's some odd figures here and there I don't have, but I have most everything since then. I also got serious about back filling my G1 and Beast Wars figures and have been spending a fair bit since.

It's been fun, though...