Minetest is great. After the last Microsoft debacle I looked into Minetest and after a bit managed to amass a nice collection of mods to make a truly enjoyable game. UIt's everything Minecraft has come to not be.
I've tried base mineclone2 and mineclone 5 and they just feel like a clunkier version of minecraft. I played Minecraft Alpha and that was more polished.
So basically, it's the minetest game with a number of additions to make survival mode more interesting or convenient (dfcaverns, mobs, travelnet, unified_inventory, ropes), some automation I haven't used yet (mesecons, digilines, signs_bot), some things that sounded cool but haven't tried yet (tubelibe, signs ) and other things that round out the world (wool, dyes, vines).
I make a small number of concessions in survival mode: occasional use of flying, XYZ location, extremely rare use of the chest of everything or /giveme. And a stratum of iron at -8 :)
My current focus is on dfcaverns- massive caves with different ecosystems that involve digging deep. For exmaple, in minetest, ores often don't show up frequently until you get to -1024, which means digging straight down and building elevators for a while.
I played Mineclone 5 for a while and it was mostly feature complete for what I wanted to do, but it doesn't play with other mods all that well, while all the mods I selected have good interoperability.