Honestly, it depends on what you're taking them for. Some people take a pre-workout thinking it will make them bigger, stronger, or faster. It probably won't, but it can certainly help you crush an important workout. And if you crush lots of workouts, over time, that can definitely help you become bigger, stronger, and faster!
Remember, the main purpose of pre-workouts is not to directly build muscle or improve your physique, it is to give you the energy, endurance, and focus to perform the exercises that can help you reach both of these goals.
There are plenty of studies showing that most of the individual ingredients in today's most popular pre-workouts provide some benefit in strength, endurance, or muscle growth. But those subjects' training history and workouts may be dramatically different than yours.
Short answer: Yes, a pre-workout can help you have a better workout. But the truth is that it's just one factor of many. Get your training right. Build your nutritional foundation. Optimize your recovery with plenty of sleep. And then use supplements to help you crush that last 5 percent of the project!