Why was Jeremy Lin undrafted coming out of the Ivy League? Well, he wasn't really that great in college. He was definitely one of the top players in the Ivy League his junior and senior years, but he was never Ivy League Player of the Year. (Sidenote: the President's brother-in-law, Craig Robinson, won that honor twice.)
Lin's college statistics are good, but nothing special: Senior year: 16.4 ppg, 4.4 rpg, 4.5 apg. His shooting percentage of .519 sounds good by NBA standards, but it's nothing special for future NBA stars, who routinely crush mortal competition their last year in college. Lin's percentages: .519 field goal, .341 3-point, and .755 free throw were all fine, but hardly eye-popping. He led the league in steals, which is a sign of quickness and floor sense, was second in assists, but only sixth in assists to turnover ratio.
Lin's senior year, the Ivy League award winner, unanimously, was Randy Wittman, who led Cornell to the third round of the NCAA tourney, with upsets of #5 and #4 seeded teams. Where is Wittman now? He's playing professionally ... in Poland. Must be bias against Wittman ... except his father Rick Wittman is now in his third NBA head-coaching gig, this time with the Washington Wizards.
Generally, Ivy League Player of the Year winners don't make it in the NBA. Matt Maloney in 1995 was the last to have much of an NBA career, once scoring 26 in a playoff game.
So, Lin looked like a very good all-around player, but with little statistical evidence that his game would translate to the next level. When I was at Rice, one year our best player was a senior named Elbert Darden, who averaged 20.1 ppg., and was honorable mention All American. He was a good guy, on and off the court. Back then, they used to have seven rounds to the NBA draft (now they have only 2, right?). He wrote a letter to the NBA saying, "Please don't waste a draft pick on me, I'm going to seminary school to be a minister," which he did.
Anyway, I suspect Ivy League basketball has slowly gotten a lot better over the years, due to the Ivy League's role as the gatekeeper to Wall Street jobs, which have gotten so much more remunerative than any other career. If you've got a good head for numbers, why not go Ivy League now that Ivy League financial aid is so lavish? So, Ivy stats shouldn't be discounted as much as in times past.