Here's my honest opinion in its entirety.
Things To Say About Minecraft:
Minecraft itself is a very open and customizable game. It leaves an infinite amount of possibilities with construction and the easy creation of mods to make the game whatever you may desire. It is one of the few games where literally almost anything is possible. You can customize uis, add completely new content, and most importantly, build anything and everything you could ever want to.
The major downsides to minecraft are that it's built in graphics can be offputting to new minecraft users who seek HD quality games, and generally it requires more knowledge of computer files than runescape does (However little it may seem to veteran miners).
Things To Say About Runescape:
Runescape generally has a larger community, not because more people play it but more people are forced to be on the same world. This can have positive and negative effects. I think runescape is so popular because it has a very broad endgame potential, greatly depending on what you wish to accomplish. Unlike other MMOs runescape doesn't make you choose one path (For mains at least), one day you can be working on slaying monsters and the next you may feel like watching netflix and chopping some trees, both of which count towards a similar goal of the game. Another great aspect of runescape is that your work is essentially saved for eternity. Someone can quit runescape for a decade and come back where they started, where as a minecraft player may have switched computers or lost their .jar or something.
Runescape is also easier to play. Runescape it self (Pre-eoc) has little to no FPS qualities. It was a click based game and combat was very point and shoot. Everything you need is on your mouse and rarely are you put in a situation, while just walking around, where intense reaction is needed. This can be appealing to some players however for those who seek a larger scale of interaction with their game this concept may find itself to be dull and generally inferior to games like minecraft.
Overall I think that they are incomparable in quality simply because the games are two completely different monsters. It would be like comparing a book to a song or dance. In general I think that runescape gives more of a sense of achievement most of the time where as minecraft is more immersive in its gameplay. But even these comments aren't true for all people, I know I've spent months playing on a minecraft server where I played with many other players and felt like i achieved much more than I ever have on runescape. The same goes for runescape, for those of you who like high risk, max combat pking, or whatever it may be, you may be interacting with your prayers, food, special attack, and other pk/pve tactics much more than an average vanilla minecraft peaceful difficulty player.
So yeah. Minecraft is better kthxbi=|