Your statement that you can't compare eras might have been more compelling if you hadn't gone on to do just that by rubbishing Sampras' opposition, boosting Roger's and saying that Pete never would have won 14 slams in this era.
Let's have a fair look at Sampras' opposition
Wimbledon '93: Agassi, Becker, Courier
US Open '93: Chang, Pioline
Aus Open '94: Courier, Martin
Wimbledon '94: Chang, Martin, Ivanisevic
Wimbledon '95: Ivanisevic, Becker
US Open ''95: Martin, Courier, Agassi
US Open '96: Corretja, Ivanisevic, Chang
Aus Open '97: Muster, Moya
Wimbledon '97: Becker, Pioline
Wimbledon '98: Philippoussis, Henman, Ivanisevic
Wimbledon '99: Henman, Agassi
Wimbledon '00: Rafter
US Open '02: Roddick, Agassi
Wimbledon '03: Roddick, Philippoussis
Aus Open '04: Hewitt, Nalbandian, Ferrero, Safin
Wimbledon '04: Hewitt, Roddick
Us Open '04: Agassi, Henman, Hewitt
Wimbledon '05: Hewitt, Roddick
US Open '05: Hewitt, Agassi
So unless Hewitt, Safin, Ferrero, Roddick, Nalbandian and old Agassi are better than Becker, Courier, Rafter, Chang, Ivanisevic, Martin and young Agassi you're attempt to put Pete's opposition down is surely flawed.
Finally, surely you cannot be serious saying that Roddick is the equivalent of Agassi
. Roddick is the equivalent of Ivanisevic, if anything.