Below you'll find links to every month's chart.
The Power Charts were a regular feature in Nintendo Power magazine starting with the first issue in mid-1988. Initially, every month there was a list of NES games ranked in order, aka the Top 30. Several months after the introduction of the SNES, it was reduced to a top 20 for all three Nintendo systems at the time (NES, SNES, Gameboy). That change occurred in January 1992. The NES charts continued all the way through 1994, which is fitting because the last NES game was released in December of that year. Only 10 games reached #1 over the 6.5 years, with Mario 3 and Zelda 1 dominating (38 and 16 total months respectively).
How were the charts compiled? The old issues with the top 30 show exactly how it worked. There were three separate rankings for players, pros, and dealers; when the the points were added up for those categories which gave us the final rankings. Issue 50 explains the process clearly:
"Each month we collect information from three sources to find the Top 20. The Players' Picks come from the Player's Poll cards sent in each month, the Dealers' Picks are based on retail sales reports, and the Pros' Picks are collected from game evaluators at Nintendo. All three sets of votes are set at equal weight, then averaged to find the point total a game receives."
The old issues (before 1992) where that additional data was displayed were nice, because it let you see how much of each game's total was in each category. It also allowed for some double checking. For example, Super Mario Bros. 2 was on the charts for every issue from #2 to #64, with the exception of vol. 23. Looking at the three categories, it's clear that they just simply forgot to include it on the charts because the points were more than enough.
For those older issues, I've listed two versions of each chart. The first is exactly how the chart looked in Nintendo Power magazine. The second is the "real" chart, as it should have looked with all errors and typos corrected. Under the real chart, I've also listed every game which earned points in addition to the overall top 30. A game must have made the top 30 of one of the three categories to earn points.
I've also come up with an overall ranking that encompasses the entire chart run from 1988-1994, which you can check out in the two links below. For every month a game was on the charts, I've given it 30 points for 1st, 29 for second, and so on. For the early issues where the magazine (and therefore the chart) was published bi-monthly, I've doubled the amount of points since the ranking was for two months. Volume 20 was the first to count normally.
I should also note that there were no charts for volumes 13, 15, 17, and 19 because those issues were strategy guides.
Total Points Ranking 1988-1994Each Month's NES Power Chart