Beat this.
Mega Man 10
I think overall this is probably the best classic Mega Man title in terms of difficulty balance. It's not too difficult in that it's cheap (MM1 I'm looking at you), but it's no cake walk either. The interesting thing about MM10, however is that its challenge mostly doesn't come from the platforming itself, but the enemies you fight. Compared to other classic Mega Man titles, this game is probably the most action-based title in the series.
You can see Inti Creates influence flow throughout every section of this game. Whereas MM9 was mostly a return to the basics for classic MM, MM10 manages to merge both classic MM an modern MM (particularly the Zero series) formulas into one cohesive package: you'll have multiple routes you can take in the game (just like in the Zero games) each route with varying degrees of difficulty, there are multiple modes and incentives to replay beyond "I want to beat this without getting hit once", its features multiple characters each with their own play style, and the game is far more action-based compared to its predecessors.
One thing I'd like to mention is the creative level design. I think this game missed some potential in regards to platforming, but I think it makes up for that in the fun levels it has. Pump Man and Solar Man in particular are probably some of the coolest stages in the whole series, and the Wily stages are the funnest I've had in the series since MM3's: not too long (MM4 and up), at least 6-7 different mid boss fights (some are straight fan service!), and varied level design.
Honestly, if there's one thing I dislike about the game beyond the fact it could feature better platforming, it's the robot master weapons. They're honestly not all that fun to use. In games like MM2 and 3 I tend to make certain sub-weapons (quick shot, metal blade;etc) my main weapons because they're such a blast to use. Then again, that's not being fair to MM10 because outside of a few MM titles, this complaint is universal for me.
The music is hit and miss but when it hits, it really nails it.
High replay value, fun level designs, decent challenge, great music...I think it's safe to say I doubt few games will nearly as fun as MM10 this year, and I haven't even touched Proto Man, Hard Mode, or Time Trial mode yet.
In a futile attempt to try and rank these games after the release of MM10:
MM2=MM10=MM3 > MM: Powered Up > MM6 > MM9 > MM5 > MM7 > MM1 original > MMnB > MM4 > MM8
As for the future of MM, I really hope that we can get some new MM titles that aren't within the classic MM bracket or one of those stupid Star Force rpgs sometime soon, because I think there's a distinct lack of Mega Man action on my handhelds in the past two or three years.