Actually, I really have thought about starting a topic just like this recently, although narrowing it down to 1967, 1968, 1969, the best years for psychedelia, I think.
Yes, that is a nearly impossible question, I've thought about it thoroughly, with runners up of 1969, 1970 and 1968, I might say my year is 1972, which might just surprise many. My reasoning is: Long John Silver (I don't care, I love that album), Dark Side of The Moon (Pink Floyd toured it through '72, at least), Thick As A Brick (Jethro Tull), Machine Head (Deep Purple), Burgers (Hot Tuna), Demons & Wizards/Magician's Birthday (Uriah Heep), Argus (Wishbone Ash), Harvest (Neil Young), Fragile (Yes), Trilogy (E.L.P), Seventh Sojourn (Moody Blues), Vol. 4 (Black Sabbath), Made in England (Atomic Rooster), Muswell Hillbillies (Kinks), Squawk (Budgie), Bulletproof (Hard Stuff), Octopus/Three Friends (Gentle Giant), Can't Buy A Thrill (Steely Dan), III (Black Widow), and I believe there'd still be time to catch shows from The Who, King Crimson, the Dead, Guess Who, Genesis, Stooges, MC5, Pink Fairies, Buffalo, Thin Lizzy and many, many others others. And yes, I am well aware that list will make many here very uncomfortable.
Hide, Witch, Hide!
The Good Folks come to Burn Thee
Their Keen Enjoyment hid Behind
The Gothic Mask of Duty!