Dh turned out well as an only child (he cooks better than I do and his mother taught him how to do his laundry and be a gentleman) and I am the oldest of four children who are widely spaced.
I was five years old when my brother was born. I think it would have been better had I been at least a year or two older when he was born. I was old enough at 5 to know that I wanted a sister, not a brother; and to be disappointed that he couldn't do anything while not being really old enough to understand WHY he couldn't do anything with me...
When my sister was born I was 9.5 and I adored her! She and I were always very close and I enjoyed helping out with her a lot. I think that spacing was a lot better for me personally, though it may have been different had I been an only child for all those years.
When my other brother was born I was 11.5 and I really enjoyed helping out with him as well.
So... I do think that large spacings can work. Please prepare your older child for the fact that the new baby really won't be much of a playmate for at least a year because I believe that was the main thing I had trouble with as the much older sibling.
With an only child, my dh says that it's most important to make sure that your dc gets to have a lot of playdates and friends over. He had a best friend (2 years younger) who lived next door from the time he was 6 years old and I know that having a neighbor boy to play with all the time helped keep him from being lonely or wishing that he had younger siblings very often.
I would play it by ear depending on your specific situation. I'm sure whatever you decide will be just fine

love and peace.
