Well landmarks doesn't mean the same thing as greatest games, gross revenue is a factor, because that can be very impactfull, but only if it spans across a lot of time, so the best selling game of that year isn't necessarily a landmark, especially if it didn't create a new standard or stand out in a different way.

Having said that, yes the list is still personal because I had to cut somewhere, and I have forgotten things as well. My knowledge only goes so far and I only did extra research for about half a day.

But a lot is based on factual data.

and thanks for calling it a great list, i hope you weren't being sarcastic :)