I voted the first two (Turn-Based only, Real-Time crap don't cut it) because that's what's most important and most difficult to pull off.
Still, last two are important as well.
- Reactivity, believability/authenticity, and C&C
- Exploration and a varied, interesting game world
Good exploration, like in
Might & Magic III: Isles of Terra is also important, I'll add great sound effects and music into that category (Exploration & Immersion).
A nice setting enhance the experience, like PST's or Dark Sun's ones.
As for the last one, Authenticity & believability is the most important as it could ruin an otherwise good game for me or at least turn it into a far lesser experience, then C&C and reactivity.
A perfect cRPG would do all four: Great Tactical TB combat, Deep and meaningful character creation and development, Exploration & Immersion and Reactivity, authenticity & C&C.
But it doesn't have to succeed on all four to be a great game.
On the other hand, fucking exploration up, like making it a walking simulator with too much backtracking and tedious traveling and/or too many containers to open for no reason (just put more loot in 4 times less containers) can ruin an otherwise decent game.