It's all subjective, so it's hard to detail, but a good Uber ride is a far more enjoyable experience than, say, a taxi ride. The driver is courteous and knowledgable, receptive to conversation if I desire it, and quiet if not. The car is in good condition, with plenty of room, typically with some bottled water available if I'm thirsty. Shows up quickly, easy to find. Driver knows how to get where I want and gets me there in a reasonable amount of time. Etc. etc.