Oh boy! this can be a never ending discussion. So I'll try to keep it short and simple - my opinion for the most part is based on how much I enjoyed driving a certain vehicle but to generalize it, I'll include Reliability, Drive (Handling and Comfort) and Maintenance. To me some certain aspects take precedence over others mainly because they compensate for any shortfalls.
Japanese manufacturers i.e. Toyota, Honda, Nissan, etc. they're probably the most reliable and durable vehicles on the market but they're the least enjoyable, Toyota and Nissan specifically, Honda is much better in terms of how it handles. Toyota across the board is ridiculous in terms of how they drive, in my perspective they swim on the road, and you have to constantly ensure they stay straight in lanes except Tacoma, 4Runner or Land Cruiser - 4Runner is probably the best Toyota I have driven and is on my list to purchase. Maintenance wise, they're not hard to work on and replacement part prices aren't that steep either (compared to Germans).
German manufacturers i.e. Mercedes, BMW, Audi, VW, etc. they all in general are great in terms of luxury. There are variations in terms of how they drive, each manufacturer is very different, VWs (GTi, Golf R, & CC) are very nimble and quick, BMWs are very engaging and responsive, Mercedes is luxury, Audi has a bit of everything but not enough. Driving a BMW (E46 M3, E46 330i, E60 M5, E90 M3, E70 X5M, F85 X5M) or VW (GTi, Golf R or CC specifically) were the most engaging and enjoyable driving experiences I've had. BMWs are very aggressive in terms of throttle response and I love how they handle, I drove an E46 M3 and I was sold to BMW for life - Mercedes is great when it comes luxury and comfort but I never found them to be responsive and engaging. Maintenance wise, they come with a maintenance intervals, and you have to follow them if you want them to last, regular oil changes, regular transmission fluid flushes, plugs replacement, etc. etc. - each of these are expensive and not a lot of people want to spend that sort of money, so they end up getting traded in, sold, going to indy shops or some people just keep driving them until they die with whatever issues they have, so long story short, if they are maintained, they're amazing and don't get me wrong, they do require a lot of maintenance, a lot more than their Japanese counterparts. Every now and then I come across 3 series, 5 series, E classes, S classes, and so on, that are one owner cars with over 100-150k miles and a pile of maintenance records, so in short, if they're maintained they'd last you while but if you cheap out, they'll become a headache or a money pit. Lol and their parts are expensive compared to Japanese vehicles but in the US, there several sources for OEM or OE spec parts or used parts for that matter, so being handy is great and you can fix things that might break your wallet at the dealership.
American manufacturers - honestly speaking, I have driven a lot of them from Mustangs to Explorers to Focus and what not, but I've never really considered owning one because I never enjoyed driving them, they do have issues like any other manufacturer and their lifespan is limited to 90-100k miles, and they will have issues - the only and the biggest plus is that their parts are probably not as expensive as other manufacturers.
I've also had a Maserati Ghibli - what an $85,000 trash it is (maybe that's why they call them poor man's sportscar).
Anyway, let me know if you'd want to dig deeper into anything - I'd be more than happy to. In short, every manufacturer has pros and cons, you have to pick one that suits your situation best.
