The best replacement for d90 is d300.

The best alternatives to d90 are rated as following:
★★★★★  d300
★★★★★  d7000
★★★  d5100
★★★  d200
★★★  60d
★★★  d5000
★★  d3100
★★  t2i
★★  d7100
★★  canon 50d
★★  d700
★★  d3200
★★  d5200
★  d80
★  50d
★  d5300
★  d60
★  nikon d5000
★  d3000
★  d600
  7d
  canon
  40d
  t3i
  d40
  550d
  nikon d7000
  d610
  d800
  d70
  d2h
  d50
  500d
  nikon d5100
  nikon d300
  canon t1i
  k-r
  t4i
  canon t2i
  t1i
  d300 nikon

Your alternative for d90 is not listed? Suggest!
Speaking about d90, one probably shouldn't forget about 50mm 1.8d.

Other search terms related to d90 and their ratings are:
★★★★★ 50mm 1.8d
★★★ sb600
★★★ 50mm 1.8
★★★ 24-70
★★★ tokina 11-16mm
★★ sb-700
★★ 50mm
★★ 35mm
★ mb d80
★ 85mm
★ sb700
video
manual lens
d5000
You have in mind a companion for d90 and it is not yet here? Propose!



Google Trends

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d90
d300
d7000