I’ve blogged before about there being no “correct” way to visualize a dataset. The video below shows how this is the case. Even when data is extremely simple, there are many ways to view it, each being better at answering a different question.
Conclusion? The trick isn’t to think “a line is the best way to show time data.” It’s to consider the question you want to answer. Manipulate and play with the data until the answer is clear.