What type of graph should I use to compare speeds of how long it took for something to boil?

Seems like a simple X, Y time verses temperature should do it.

I still don't know what type of graph you're talking about. Nevertheless, how do you make it on Microsoft Excel?

Temperatures in one column, time in another, make a scatter graph.

How do you make a scatter graph?

Click the graph button, choose XY (Scatter) :p