Just caught a Deoxys on Leaf Green so its the defense version here are its IV's at level 78. Are these IV's good enough or should I reset for better?

HP IV: 28 [27 ~ 29] 48%
Attack IV: 25 [25 ~ 26] 96%
Defense IV: 18 [18 ~ 19] 95%
Sp.Atk IV: 30 [30 ~ 31] 97%
Sp.Def IV: 21 [20 ~ 22] 48%
Speed IV: 18 [18 ~ 19] 95%

I'm intended on using it on Fire Red so it will change forms when I trade. Its nature is Lonely and I intend on using it as a Choice Band Deoxys-F.

Seems to be pretty pretty good attack and special attack IVs, which are the most important ones. Overall average or above average in every stat. It's up to you, but I'd use it, I don't think you're likely to get one that good in a while.