(I know this POV is almost "sacrilegious" here, but ...) I believe those who place Sampras on the same level of Laver and Borg are influenced by their own sentiment.
I don't think so many writers who know more about tennis than we could dream of, that place Sampras along Laver & Borg are biased. Steve Flink(who is one of the most knowledgable writers on the history of tennis) in his book Greatest Matches of the 20th Century(great book for those that want to learn more about the history of the sport) ranked Sampras at #1, above Borg & Laver in his 'best players of the century' list. And this book was published at the end of '99 when Sampras 'only' had 12 majors.
I think you & AndrewD are getting too caught up the 'most majors' part of Sampras as being the only reason he is regarded so highly.
As urban & chaognosis(2 of the best posters here & probably the most informed as far as the history of the game go) have said many times the fact that Sampras won 7 Wimbledons & was #1 for 6 years are the most important aspects of his career, not the total majors part.
Since the beginning of the century, Wimbledon has been the most important title in tennis. Winning it multiple times is a major factor in ranking great players. When Borg won 3 straight '76-78(eventually 5) it was a monumental achievement, since no one had done it since Fred Perry. Sampras was the 1st to 3 peat after Borg & the 1st to 4 peat. A player that won 7 Wimbledons in any other era would be an instant candidate for greatest ever. Imagine if Jack Kramer, Don Budge, Tony Trabert or anyone did that in the 40s/50s. We'd still be talking about it, there would a statue of them at the US Open. Sampras won more Wimbledons than Becker & McEnroe combined! That is an amazing fact, considering those guys were so great on grass.
Also the #1. Yes the computer only started in '73. But there was a yearly ranking list since the 20s put out by international tennis writers. Sampras' 6 straight years would also be a monumental achievement in any era. Not sure if anyone has ever been #1 for longer, at any point in history.
I think you may be a bit biased if you don't consider Sampras on the level of Laver/Borg, you can't dismiss his achievements which would be highly regarded in any era.
One other stat on Borg/Sampras. In the open era, only Borg & Sampras have won majors in 8 straight years. No other player had even done this more than 4 straight years.
Sampras & Borg are the only open era players to win 4 or more majors at the same venue twice(Sampras at W & US, Borg at French & W)
And far as longevity goes, Sampras & Rosewall are the the only players in history(not just open era) who won majors as a teenager, in their 20s, & in their 30s)
Sampras was also #1 seed at 23 majors in the open era, a record. Lendl was 2nd with 18.
A player of Sampras' calibur is a rare thing, I think that Federer (another rare champion) has come along so soon after had made many fans forget this. Also you might be biased because Sampras' game is "one-dimensional" as you've said earlier. Maybe it is(many said the same about Pancho Gonzalez), but that can't change the fact that his resume is almost unequaled in the history of the sport.