The HOF isn't based entirely on stats but thay are a big part of the evaluation. So I decided to look at the most likely HOF candidates that aren't in.
Receptions Witten 1228 Gates 955 Kelce 730 Gronk 621
Yards Witten 13046 Gates 11841 Kelce 9328 Gronk 9286
TDs Gates 116 Gronk 92 Witten 74 Kelce 60
Yards/Rec Gronk 15.0 Kelce 12.8 Gates 12.4 Witten 10.6
Yards/Target Gronk 9.7 Kelce 9.1 Gates 8.1 Witten 7.6
% of catches for 1st downs Gronk 75.52% Gates 68.9% Kelce 68.08% Witten 54.07%
all stat from player pages on pro-football-reference.com
There's no objective way to evaluate blocking but and Gronk and Witten were clearly much better than Gates and Kelce.
In terms of playoff performance Gronk and Kelce are well ahead of the other 2. Among all players Kelce is 3rd in Playoff Receptions Gronk is 4th, Gronk is 3rd in Rec Yds Kelce is 5th. Gronk is 2nd in TDs Kelce is tied for 3rd.
Playing on a lot of winning teams makes a difference so again Gronk and to a lesser extent (at least for now) Kelce have the advantage. Gronk 4 rings (although he was injured during the playoffs for 1).
Maybe they shouldn't count it but personality, charisma and Fame also seem to affect the voters. After all it is called the Hall of FAME not the hall of great players. Not much of an argument on who has the advantage there.
Gronk is the most likely to be 1st ballot, the other 3 are all worthy of induction, but a lot of players end up having to waait their turn.