College students are arriving on campuses with ratcheted-up expectations for the aesthetics and comforts of their residence hall rooms. And increasingly, colleges are scrambling to meet student expectations in the hope of luring top applicants. Across the Boston region, overhauls and construction are underway to add elan to campus living. Harvard University is planning an ambitious overhaul that will gut and renovate a dozen buildings. At Boston University, a $100 million pair of towers is under construction next to another pair that opened in 2000. The Massachusetts Institute of Technology six years ago opened the architecturally hailed Simmons Hall with custom-made Scandinavian-style furniture and walls of windows in the rooms. Plasma screen televisions, wireless Internet, and surround sound are now standard-issue in 80 percent of Boston College dorm lounges. Northeastern University has opened 11 new residence halls since 1999.