Wow - truly a mixed bag of replies here.
First off, Duncan - everyone starts somewhere. As this is only your 5th post, I will assume that you are somewhat new to the whole collecting thing. Not a bad start, but it's just that, a start. If you are collecting truly popular games, you have a great start. If you are trying to get them all, you have about 800+ to go. Either way, stay positive and have fun!
Second, some of the other comments are just flat out rediculous, and can only be made by those who have no clue what they are talking about. Take a look at all of the resources available to you - the DP Guide, Etler's rarity list, etc. and come up with the best idea of what is rare (or at least genuinely hard to find.) I am sick of people saying that the Dragon Warrior series is RARE, or the Mega Man series is RARE, because it simply is NOT TRUE! These games are pricey (especially with box/manual, etc) because they are excellent games that everyone knows were lots of fun. High demand with a high supply can also raise the price - it doesn't make them "rare". Try getting the three Panesian games - you will understand (equally) that short supply can also raise the price, but is a true indicator of rarity.
Finally, don't take the Etler list as "GOSPEL". Mike created that list in assembling his own collection. In doing so, he rated the titles according to what difficulty he had in finding them (especially in his local area.) Just use it as a guide. There are MANY A rated titles that you can probably find every day of the week on eBay. There are others though, that you may not find for a month - and they are rated B or lower (I speak from personal experience.)
I'm sure that there are many ideas of what "collecting" is - and it's all personal. I would personally play just about EVERY game on your list Duncan - so if you goal is to have a great playable NES collection, you have a great start. My personal goal is to have a collection of every TITLE, complete in the box with whatever it was originally packaged with.
Good luck.