Never has there been a more diverse package of the good and the questionable than the Mega Man Legacy Collection. There are some games from Capcom's early days with the character that I love and cherish. But there are others that I can't bring myself to enjoy.
Obviously the first one isn't really very good (which is why they remade it years ago), but it was at least trying a lot of different things. Not all of them stuck. The biggest offenders were Elec Man's vertical stage, Ice Man's block puzzle having death traps, and don't get me started on the Yellow Devil, a boss it's almost impossible to defeat without exploiting a glitch.
Mega Man 2 was a huge improvement (in my eyes, it's the best of the older games) with better bosses, coherent level design, and some of the best music in the whole series. That and Mega Man 3 are worth the price you pay for the collection alone.
Of course, you'll also be getting 4, 5 and 6. All the Mega Mans. Mega Men. For my money, that's where the series started going downhill. 4 introduced the chargeable buster shot, but didn't have levels designed around it; 5 fixed some of 4's issues, but also became too easy for some tastes. 6 is... fine, I suppose. Capcom saw bigger things on the horizon at this point, with Street Fighter II being a global sensation and Resident Evil just around the corner. But it's good to look back at their beginnings (even if their heart wasn't in it towards the end).