食べ物 - appropriate as written or spoken language, a basic word, commonly used in speech
食品 - food product, think of a packaged food product on a shelf in the store
ご飯 - literally rice (polite), used to refer to "a meal" as in breakfast, lunch or dinner
食事 - a meal, frequently used in hotels and restaurants as 「お食事」 (おしゅくじ)
〜物 - assuming you mean 揚げ物 (fried food), 煮物 (boiled food), 干物 (dried food), etc... these are self explanatory, just more specific.
Also don't forget:
食物 (しょくもつ) - Mostly in written language, "food stuffs" is a good English equivalent
And just to whet your appetite (pun definitely intended) here is a breakdown of common food categories.
Animal Food Products (動物性食品)
肉類 (にくるい - meat, incl. poultry)、魚介類(ぎょかいるい - seafood)、卵類(らんるい - eggs)、牛乳(ぎゅうにゅう - dairy)
Plant Food Products (植物性食品)
穀物(こくもつ - cereals)、豆類(まめるい - pulses)、芋類(いもるい - tubers)、野菜(やさい - vegetables)、山菜(さんさい - mountain vegetables)、海藻(かいそう - sea vegetation, seaweed)、種実類(しゅじつるい - aw nuts)、果物(くだもの - fruits)、ハーブ(herbs)
(ref: http://ja.wikipedia.org/wiki/%E9%A3%9F%E5%93%81)