I did a similar thing a couple of years ago. "Replayed" the whole series before playing Halo 5 (, which I'd owned for years but never played). I had an Xbox One X and wanted to see the series in the best way possible. Technically I was playing a few games for the first time, previously, I'd only beaten Reach, 3, and 4. During the replay, I only played 1-4, ODST, and 5. Reach was still being added to the MCC.
I didn't appreciate how good the series was the first time around. In fact, or seemed a bit overhyped and confusing. During the replay, everything fell into place.
Still never finished a "Wars" game, though.
From best to worst
Reach, 3, 1, 2, 4, 5, ODST. All were great except 5.