Ganesh is the most respected and loved of all Indian Gods. He is found at the the entrance of most temples in India because, before you do any puja you must worship Ganesh to ask him to remove all obstacles that are maring the prospects of success in the worship you are about to perform.
Ganesh stands at the portals of heaven and will clear the way with his great big trunk for a good reincarnation. Ganesh was born from his mother Parvati as she bathed - you see her train of thought went so.....: "I am doing my ablutions but I have nobody to protect me from unwelcome intrudors. My husband Shiva is always engaged in his meditations - what I need is a good strong son to protect me." She scraped the sweat and grime from her body and with this she created her son Ganesh. Ganesh grew into a lovely intelligent God child and dutifully protected his mother. So much so, that when Shiva, his father, finished his centuries long meditations, Ganesh never having met his father, refused him entry into his mother's apartments.
Shiva being Shiva, with one mighty swipe disposed of the little upstart that dared refuse him entry into his wife's apartments. Parvarti, hearing all the commotion ran outside to find her husband standing there with the lifeless body of her son "oh lord of all the heavens what have you done?" was her woeful cry. Shiva, realising his mistake, vowed that his son would receive the head of the first living being to pass by and thus regain his life. It just so happened to be an elephant and that is why Ganesh has his elephant head.
If you want to be nice to Ganesh give him LADUS (India sweet sort) he is crazy about them and that's probably the reason why he has such a rotund belly!