"Kochać" is definitely 'to love', for some contexts I'd recommend 'uwielbiać' ('to adore'), but still that's a personal choice: obviously it's natural to love your parents, can work with friends if you really feel like that; dog, car - again, if you would say 'love' in English, nothing forbids you from saying that in Polish. But it really is a word full of emotions, so you'd need to be really emotionally connected with your dog, or with your car (in English you probably could say "I love it!" about a new car, it's hard to imagine using it like that in Polish).

I can also imagine someone says "Kocham Michaela Jacksona", if they really loved his music and him as a person, although in a context of an 'idol', a celebrity, I'd go for "uwielbiam".