I absolutely loathe Sampras, but nobody can make a serious argument for ranking Borg above him.
Borg won 11-27 (40.7%) of his slams while Sampras 14-52 (26.9%). Borg showed up to AO once or twice in his career and would've won more slams than Pete if he had played in more slams and not retired at the age of 25. In addition, he was the reigning FO champion and could've won more titles. Borg displayed greater command of surface disparity by winning the fastest and slowest slams five or more times each. Sampras greatest success was in fast hc, indoor carpet, and grass. At minimum, Borg made 3 HC finals and Sampras not even 1 FO final. Overall, Borg is 90% in GS matches compared to 84% for Sampras. Borg has 82% winning percentage compared to 77% for Sampras.
National Representation is not even close. Borg's Davis Cup record runs circles around Sampras. Borg was 37-3 in Davis Cup and 9-2 versus prior or future GS champs while Sampras was 15-8 and 3-3 against GS champions. I'll give Sampras credit for that great DC run in clay when he won in Moscow, but he also had an early exit in the 1992 Olympics.
Year-end-Finals this goes to Sampras as he won 5 titles (4 Carpet, 1 HC) and also added a couple of Grand Slam Cups. Borg also won two Grand Prix and a WCT Final, so he did have success there as well.
As for h2h against main rivals Borg had winning records against all his main rivals as Connors, Vilas, Orantes, and Nastase. Newcombe (2-3) and McEnroe (7-7) toward the end were the only players that got the advantage in their rivalry. Sampras had a losing record against Krajicek, Hewitt, Stich, Roddick, Bruguera, and Haarhius (to name a few).
If someone thinks Sampras > Borg that is okay, but to say
no serious argument for Borg is a bit preposterous.