I feel like I have no real brand or model loyalty, but I do come back to some platforms over others. I actually made a list a few years back to help me keep track of everything I've owned over the years:
1991 Geo Storm (first car, I beat the hell out of it)
1996 Mitsubishi Eclipse (second car, it beat the hell out of my wallet)
1991 Toyota MR2 Turbo (drove too hard and turned into a money pit)
2004 Subaru WRX (my first brand new car)
2003 Nissan 350Z
2006 Mazdaspeed 6
2006 Subaru STI
2007 Infinity G37
2007 BMW 335i
2010 Mazda 3 hatch
2011 VW GTI
2012 VW Golf R
1990 Mazda Miata (that's where it all really started...)
2013 Infiniti G37x
2014 Ford Focus ST (I bought that car for $19k brand new- should have kept it!)
2004 Mazdaspeed Miata (Miata #2... I REALLY should have kept this one)
2015 Audi A3
2015 Subaru WRX
2016 Golf R (hands down, one of the best daily drivers I've ever owned)
2017 Ford Focus RS
2007 Honda S2000 (where I found "the Miata on steroids")
2018 Honda Civic Si (another car I probably should have kept)
2019 Jeep Wrangler
1992 Mazda Miata (Miata #3...)
2008 Honda S2000 (I still own this car- longest a car has ever been in my garage, potentially my "forever" car)
2020 Tesla Model 3 Performance (made every other car I've ever owned feel underwhelmingly slow- yet, wasn't as much fun as an NA Miata)
1994 Mazda Miata (Miata #4...)
2003 Jeep Wrangler
2021 Honda Civic Type R
2021 Mazda 3 Turbo (also a lovely, criminally underrated daily driver)
2009 Mazda MX-5 Miata (Miata #5... the NC became my favorite!)
1999 Mazda Miata Sport (Miata #6...)
1988 Honda CRX Si (my first wishbone Honda, I'm a couple decades late to the party)
1998 Honda Civic DX hatchback (double wishbone Honda #2...)
1996 Acura Integra GS-R (double wishbone Honda #3... current track build)
2008 Nissan Xterra (current winter beater)
2008 BMW 128i 6MT w/Sport Package (current "daily" per se)
I should mention my wife also owned a 2018 Miata as well, which would make it 7 total if we're counting spouse's cars in the mix.
As far as platforms go, I suppose I've owned more Miata's than anything else (at 6+ of them so far). But as much as I love the NA/NB, having owned all 4 generations (if you include my wife's ND1), the NC is actually my favorite. If there were more places for the NC to be competitive, I would own one right now.
But if I look at the cars that have actually spent the most amount of time in my garage, that's easy: the Honda S2000. While I've only owned 2 of them (the first one I sold for financial reasons, not because I wanted a different car), the little Honda roadster has been my preferred fun machine for years. I also spent more time on track in an S2000 than any other platform I've owned. I go through cars like some people go through socks... but my current AP2 holds the record for being in my garage the longest (4+ years). If they hadn't gotten so expensive, I would probably own 2 of them: 1 for a fun weekend car and 1 for a full track build.
Here in the past few years, I've owned 3 double wishbone Honda's (assuming you don't count the S2000's). I discovered them a couple of decades later than the rest of the world- as it turns out, they're a pretty good time and easy to work on! Who knew?!? They're probably my current "go-to chassis".
Other notable chassis I've owned more than 1 of:
-When I was young, I owned a couple of GD chassis Subaru's... that was a long time ago. Bought my first one after I came back from my first tour in Iraq. I haven't really yearned for another one since and probably never will.
-I also owned a 350Z and x2 G37's, which are technically the same platform. I have no real interest in another G37, but have considered a track build 350Z a few times. If they were allowed in NASA TT5, I probably would have bought one.
-I've owned x2 VW MK6's- a GTI and a Golf R. At the time, I thought the MK6 was the perfect daily... until I bought a MK7 Golf R. Great car if you need something that can literally do just about anything. The Audi A3 I owned is pretty much the same platform (MQB) as the MK7- I prefer the MK7. These cars are good at all the things, but I don't know if they're great at anything. I really like them a lot, but don't really love them. They feel more disposable and contemporary than many of the cars I've owned.
-I've owned both a Focus ST and the Focus RS. Shockingly enough, I preferred the ST! I would absolutely own another ST if they depreciated and the kids hadn't beat the hell out of them.
-I've also owned a 2018 Civic Si and a 2021 Civic Type R... driving them, for whatever inexplicable reason, hurts my right knee, no matter what I do (lots of seat and pedal modifications couldn't make the pain go away). If it wasn't for that fact, I 100% would have kept either of them. I loved both of them. They're just so damn good to drive! I won't buy another one, because of knee pain, but otherwise, I still regret selling both of them.
-Technically, my E90 335i and E82 128i are built on the same platform... it's been a long time since I've owned the E90... but good lord the E82 is good to drive! That car is literally good at everything!