I've never personally bought this superficial cop-out (as I see it) of labelling John a hypocrite with Imagine.
To me he's inviting everyone (himself included) to glimpse a dream of what could be do-able if EVERYONE detached themselves from materialism. It's typical Lennon simplification (you only have to WANT war to be over and it then will be, right?). But since everyone isn't willing to dream he'll play the game on the world's more brutal terms and win first. Then, from his vaulted position, tell us how it could be if we'd ALL drop our guard and play the rules of the idealistic dreamers. Classic Lennon: a sentimental hearted, naive, well-meaning guy who fundamentally wants everyone to love each other - but will ensure he gets the first head-butt in in the brawl of life, so that we'll all shut up and listen.
He seemed to see things on a grander scale than most. Someone once said Paul's optimism was always tailored in his songs to individual characters and circumstances, whereas John's positive songs were often expressed at a global level (ironically for such a personal, subjective songwriter). I think it was Liverpool comedian Freddie Starr, who knew The Beatles in The Cavern/Hamburg days, who claimed John had the beautiful vision of a poet who was always exasperated by others' limited ambitions. To paraphrase Freddie (I can no longer find the exact quote): "We all wanted to improve our lives but he wanted to improve the world."
I'd be a hypocrite myself if I criticised him over Imagine. We all have the double standard within us... I've done anonymous charity work and private good deeds in my time, but am I willing to sell my big plasma TV and give away the profits having put money in a collection tin to help the homeless earlier that day? Errrr....well, no. I love natural history and the animal kingdom but I'll happily tuck into a slice of venison without a shred of guilt.
On a grander scale I guess that sums up George, too. As nim says, he preached spirituality and genuinely believed in the higher teachings of various gurus but at the same time ensured he had the fastest cars and the biggest of mansions. We are all multi-faceted to some extent if we're honest.