It depends on your understanding of "best".Most convenient is the direct airport bus, that gets you directly to the hotel:
http://www.limousinebus.co.jp/en/timetable/narita/shinjuku_h.html
But NEX&Suica with a 5-10 minute walk from Shinjuku Station is considerably cheaper.
More options:
http://www.japan-guide.com/e/e2027.html?aFROM=2027_3011