Try any theme you like and enter one or more keywords related to this theme to see how is it trending among other people in the whole world. Watch big data at work. Just pay attention to the language you use and filter out noise-words by selecting the appropriate category (e.g. "Inventor" as software vs. "inventors" in science).
So let's try to compare popularity of the BIM software Autodesk Revit vs. ArchiCAD (last 5 years, category: software):
Or the 3D CAD modelers Autodesk Inventor vs. SolidWorks (last 5 years, category: CAD/CAM):
Or a more complex dogfight - how the recent popular buzzwords in CAD and IT are trending - BIM vs. IoT vs. 3D printer vs. big data vs. PLM (since 2004, category: computers & electronics):
The results are pretty objective due to the large number of "voters". Power to the people...