I'm stealing this idea from Jalopnik, but I've thought about it before. 1998.
My choice is based mostly on the japanese market but there are some good cars from other regions in this period as well.
I made this list for my jalopnik post but i'm copying it over.
1998
--Japan--
Toyota
-Soarer
-Supra
-Chaser
-Aristo
-MR2
-Celica GT-Four
Nissan
-Skyline R34
-Silvia S14
-180SX
-Z32
Mazda
-MX-5 Miata
-RX7
Mitsubishi
-GTO
-Lancer Evolution V
-Pajero Evolution
-Eclipse GSX
--USA--
GM
-Camaro (first year with LS1)
-Corvette
-Firebird
Chrysler
-Viper
-Neon ACR
Ford
-Mustang Cobra
--German--
Porsche
-Boxter
-993 911
-996 911
-911 GT1 Straßenversion
Audi
-TT
Mercedes
-SL600
-CLK GTR Straßenversion
BMW
-M3
-M5
-M Coupe
-850Ci
--Italian--
Lamborghini
-Diablo
Ferrari
-550
-F355
I'm probably missing some big ones. It's 5AM and I haven't slept yet.
1993
McLaren F1
Isdera Commendatore 112i
Lister Storm
Jaguar XJ220
Porsche 911 GT2 (993)
Bugatti EB110 SS
TVR Griffith 500
Mercedes-Benz 190E 2.5-16 Evo II
Honda Prelude (BB4)
Nissan Skyline GT-R (BNR32)
Honda NSX (NA1)
Mazda RX-7 (FD3S)
Mitsubishi Lancer Evolution III (CE9A)
I couldn't find more
I really like 1950-1975 cars and 2006-present cars. Everything in between is just ugly and boxy for my tastes. On occasion there might be some that I might like that don't fit in those ranges.
'78. The Galant Lambda, my first ever car ('78 Accord), my first V8 car I ever owned ('78 Monte Carlo with T-Tops) and tons of cool import things that year.
Although I guess I couldn't live without some modern car things, so it's a tie between then and '91, my birth year. Last year of the fourth gen civic (the best civic, m'rite?) and within the range of some amazing japanese machines.