So, I can't go wrong with the 6 pack. All of the better M&M games are in that bundle. How about 7 - 9? Are they any good?

Buy HOMM 2 and 3. If you like those, buy the first one, you'll probably have fun with that as well.

I enjoyed 7 a lot, although it feels more constricted on where you can go compared to MM6 (although this is probably BS). 8 I played a short while of, but recruiting characters rather than making them felt weird. 9 I haven't played (although I did buy it again here), although I've heard terrible things about it :(

If you like 6, 7 is even better, while 8 is also good-ish but rather imbalanced.

and 9... Nine is the weird game of the series, among internet dwellers there are some poeple that sort of liked it, but normal people generally don't

Does lesser also mean it's less complicated and easier to start with? I know HoMM3 is the most popualr but I haven't been able to really get into it yet. HoMM2 looks a little simpler to me and also more visually appealing (to the eye of the 90's VGA pixel art fan, that is).

Yes, it's easier and less complicated. I think HoMM 2 is a great introduction to the HoMM games. It also has some excellent user made maps made for it, of which some of the best are included in the Gold version.
Usually with strategy games only the campaign is really good for single player use, while user made maps can be far better than the original maps.

BTW, are you the same Leroux that hangs out at the FRUA forum?

Shhhhh! No, that's my evil twin brother. *cough* ;)

While I don't find 3 complicated (for the reason that I've played it for many years), still yes, you could say 2 is easier to get into than 3. One reason is that there aren't as many factions, another that your troops consist of 5 units, instead of 7 which is the case in HoMM 3. There's less of everything, from places of interest in the world to things you can build in your castle. If you find the art more appealing as well, then by all means you should favor 2 over 3. And like I said, it's a great game on its own as well. Even though HoMM 3 is universally thought of as the better game, everyone has their own tastes and are entitled to their own opinion and preference, right?