After playing all three consecutively you would immediately assume that Halo 3 was the largest in scale, but what you have to appreciate is that the players movement speed was much larger in the first game than either of the sequels, thus its easy to miss the fact that the levels were just HUGE in the first game, specifically "halo" and AotCR.
Easily my favourite of the three, oozes atmosphere that the other two just, dont.







