I love the open ended nature of this question.
You can view the question as who was the greatest heavyweight in college using only college achievements. Or who was the greatest heavyweight in college using all achievements while in college (i.e. international results). Or who was the best heavyweight in college using a lifetime of results. Or who hit the highest peak in college while wrestling heavyweight. Something for everyone.
If you only want to focus on college results, then it seems a logical starting point is to examine the list of four time all-americans first. There have been 12 wrestlers who AA'd 4 times at heavy (sorry Kyle Snyder), starting with @ionel's hero, Dick Hutton.
The case for Steveson has to be based on highest high rather than any sustained success. But if that is the criteria I think Snyder pips him. Steveson has 2 AAs, 2 titles, and an Olympic Gold while in college. Meanwhile Snyder has 3 AAs, 3 titles, and an Olympic Gold while in college. Do you ding Snyder for having his gold at 97kg, or do you acknowledge that 97kg (~213 lb) is still heavy in college?
For me I have Snyder, Steveson, Hutton, Haselrig, and Mocco as my top 5.