As a big aviation enthusiast, I love this topic.
In terms of civilian aircraft, my favourites are;
Wide body
Boeing 747 - Nothing like the big ol Jumbo. If you've had the chance to sit on the upper deck, it is fucking amazing. The most comfortable big plane still , 40 years after launch. THe economy seats still have the best legroom in my reckoning. The newer 787 just sucks in terms of leg room as well as lateral space. Its a pity to see this 4 engined big bird retire from passenger service. Magnificent airplane.
Airbus A380 - Another massive plane, the biggest passenger plane in the world. I have had the pleasure of traveling on Emirates' A380 and i have to say, the plane is amazing. Good legroom in economy and comfortable seats. For a plane with such massive engines, it is surprisingly silent. You won't see too many of these around in the next 20 years, given the economics of operating a 4 engined plane.
You have to see this behemoth in person to believe.
Lockheed Tristar - What an amazing aircraft, well ahead of its time when introduced to the market. Fly by wire, flight computers and autopilot in the 70s was a brilliant feat of cutting edge engineering. Perhaps the most comfortable wide body aircraft I have ever had the pleasure to travel in, apart from the cabin noise at the back due to the engine layout. Superb looking plane as well with the third tail mounted engine. The airframe still looks uber modern in 2021.
Narrow body
Boeing 717 - Have flown on this more than a handful of times in the states with Delta. Very nice plane to travel in, especially if you are sitting in the twin seat row. It has 3-2 seating configuration, which means no middle seat for many. Very underrated short haul aircraft and one of the few T Tail birds still flying in active service. Rear is a bit noisy as is the case with most planes with rear mounted engines.
Embraer E190 E2 - I flew this last year with Helvetic. Two abreast seating means no pesky middle seats. Amazing seats and leg space for a narrow body aircraft. Ultra modern interior with all the works. Possibly the most comfortable short haul/regional jet. The cabin is so silent, you wont know you are flying! Big windows too. Better than Airbus A220 in terms of comfort IMO.
Boeing 737 -200 - I have lots of great memories associated with this plane, especially of holidays with my family, which started with a one hour hop on this old bird. Not the most comfortable or silent, but for sentimental reasons I love this plane.