It depends on if you are talking about career at MSU, or career in MLB. I think Moreland could have had a better career at MSU had Polk not toyed with the idea of redshirting him, and basically caused him to miss half of a season. So, some of it is in the eye of the beholder. Also, I believe it was Papelbon that blew a save for MSU in 2003 to cost us a Super Regional bid.
If you're talking about strictly MSU, you have to talk about people like Frank Montgomery- 10-0 in 1962, Buck Showalter hitting .459, Bruce Castoria hitting 28 home runs and driving in 98 or even Aaron Weatherford not allowing a run until the last game of the year in 2008. Ed Easley won the Johnny Bench Award. BJ Wallace and Bobby Reed were both very good pitchers that might warrant top ten duscussion.
To me, I would say Palmeiro for both. Just because he was the first guy to win the SEC triple crown in 1984. Will Clark is a close second and he is MSU's only Golden Spikes Award winner, and he should have stayed in better shape in MLB to be honest with you. Jeff Brantley was better than Papelbon at MSU, and he also won a Fireman of the Year award in MLB. Bobby Thigpen also won the same award and set the MLB record for saves in a single season. Mitch Moreland is still starting out his career, and Paul Maholm is a solid pitcher.
As far as Papelbon goes- it's too soon to call him one of the greatest of all time. I think he could possibly get there at some point. Closers don't really have a "magic number" for saves because the closer position has evolved so much in the past 30 years like the other positions- 500 home runs, 3,000 hits, 300 wins, etc. Personally, I would say wait until he gets 300 saves or so, and then I would guess 400 would warrant HOF consideration to really begin talking. I would say the one thing about the great closers that they all have in common is longevity- Rivera, Eckersley, Fingers, Hoffman, Lee Smith, Gossage, Quisenberry, Sutter, etc.