Estimated Wins Added (based on PER):
1. Damian Lillard
2. Stephen Curry
3. Kyrie Irving
4. Kemba Walker
5. Russell Westbrook
6. Mike Conley
7. Ben Simmons
8. Jrue Holiday

Wins Over Replacement (based on Real +/-)
1. Damian Lillard
2. Stephen Curry
3. Jrue Holiday
4. Kyrie Irving
5. Mike Conley
6. Kemba Walker
8. Russell Westbrook
11. Ben Simmons

Win Shares
1. Damian Lillard
2. Stephen Curry
3. Kyrie Irving
4. Mike Conley
5. Ben Simmons
11. Kemba Walker
12. Russell Westbrook
15. Jrue Holiday

VORP (based on Box +/-)
1. Russell Westbrook
2. Damian Lillard
3. Stephen Curry
4. Kyrie Irving
5. Ben Simmons
6. Kemba Walker
7. Mike Conley
9. Jrue Holiday

Average Game Score (per games played)
1. Stephen Curry
2. Damian Lillard
3. Kyrie Irving
4. Russell Westbrook
5. Kemba Walker
6. Jrue Holiday
7. Mike Conley
8. Ben Simmons

Based upon all this there is no question that Curry, Lillard, and Irving are all better then Conley and are the top 3 PGs in the NBA right now. Walker and Westbrook are probably #4 and #5, though Conley is at least somewhat in the conversation with them. I'd probably put Conley at #6 with Holiday and Simmons rounding out the top 8. I didn't include him in the rankings in this post but Kyle Lowry was probably next best after that, though clearly behind those other 8 statistically. To recap more concisely:

1. Curry
2. Lillard
3. Irving
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4. Walker
5. Westbrook
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6. Conley
7. Holiday
8. Simmons