I'm certainly not qualified to answer that question myself, but it saddens me to see a thread go unreplied. Everything I've read or heard about diet suggests that variation is key, and people bang on about different colours of fruits and such. On the flip side, I gather most of what you'd be missing from non-apple fruits would be vitamins and minerals, which could probably be replaced to a fair degree with an appropriate supplement.
As I say though, absolutely don't take my word for it. I can suggest this subreddit: http://www.reddit.com/r/fitmeals
They seem to have a lot of info and some useful FAQs in the sidebar. Don't be discouraged if you're not used to Reddit's layout, it's basically just a forum where threads move up or down the order based on the voting arrows on the left.
I confess I'm always a bit sceptical of people who say they hate all fruit/veg except for X, but maybe that's just because I was raised vegetarian on a pretty herbacious diet
There's just so much good fruit. Have you tried mixed berries and yoghurt, for example? Sliced yoghurt, banana, honey and oats is another favourite of mine. And there's all these smoothies and things, and fruit salads and what have you. I don't know whether you could or couldn't get by on just apples, but I'd give other fruit a shot just to be on the safe side.