heres my personal top 5
1. balanced and rewarding pvp, with multiple pvp modes as promised
2. complex itemization allows for very unique builds and not just damage % increases
3. complex and engaging story, with unique villain motivations beyond "haha i will kill u"
4. excellent communication and dedication from development team, clearly took the time to understand what they were building upon and respected their predecessors
5. character class design went above and beyond, and not just recycled names, looks and skills from previous installments