In reply to JOHNVIDAL.

I think it does compare. I have often thought about the fact that chart methodologies have changed many times over the years, but those very inconsistencies are the reason you have to accept the results for what they are. Drake's record is every bit as valid as Michael's.
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Consider another very imprecise comparison -- Whitney Houston's IWALY (1982) to Olivia Newton-John's Physical (1981). Whitney's song sold 4 mil and topped the Hot 100 for 14 weeks in the Soundscan era. Physical topped the chart for 10 weeks pre-Soundscan (the max any single song held at #1 in the rock era before Soundscan) and sold 4 mil also. No one would suggest that Physical compared to IWALY qualitatively, but Physical was every bit as big a hit.
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You have to trust that Billboard did its best for each chart era and accept the results for what they were/are.