Tinned lychees are in my opinion an excuse for the fruit, the difference between the fresh and tinned being at least as stark as with peaches. If you can't get fresh ones I would suggest waiting until you can rather than having them tinned - at least drain all the syrup off the tinned ones and even wipe them dry before eating. I agree regarding rambutan which I actually prefer, less fiddly to peel, I find - unless very fresh the lychee skin hardens and fragments under peeling. Both fruits and more besides are quite different from so much else we northern Europeans are used to. If you are not particularly interested in fruit in general (or only very selectively) then it is a matter of how you take to something really unusual - personally I am very keen on any and all fruit with very few exceptions, jackfruit being one.