halo reach: absolute peak, phenomenal campaign and a great send off from bungie.
halo combat evolved: decent first half, anything past 343 guilty spark is complete garbage.
halo 2: significant step up over ce, bit long but still more enjoyable.
halo 3: very good, definitely my 3rd favorite
halo 3 odst: 2nd favorite easily
halo 4: felt like an assault on my eyes, terrible game never gonna touch again.