It is impossible to say whether or not most people are happy today, but you can look at some factors that show that there are a lot of unhappy people. Depression is the largest mental disorder out there, with many people never even seeking help for it. Anti-depressants are a billion-dollar industry, and suicide rates are very high. Even though we have every comfort that we could desire, these factors seem to indicate that happiness does not come with technology or lifestyle. In Fahrenheit 451, they had all of the comforts and technology that the could desire, but the problem was that they had lost sight of what really mattered: family, meaningful, deep relationships, simple beauties and truths, independent thought and debate, and self-directed fulfillment. Instead, they drowned out any thought or progression with entertainment.
There is a definite difference between superficial happiness and true peace and joy. After we watch a good movie, or play an awesome video game, we might feel happy on the surface. But take those things away, and are we content? Our society needs to realign itself with the ability to feel strong, confident, assured and joyful, without all of our gadgets, comforts, movies and games. Think of the last funeral that you went to--what was the focus? It was on the family ties and friendships that a person had made. It was on that person's ability to influence the lives of others around them for good. This is what life is about, not reaching the next level in video games or having the coolest gadgets. In Fahrenheit 451, the people had lost sight of true connections and true independent happiness. And, I see a lot of those same conditions in our society today. I don't think it is as bad as the novel, but, it does get worse and worse as time passes.
I hope that those thoughts help to get you started; good luck!