You think Horizon looks amazing? It's a noticeable downgrade graphically from Forza 4 (which makes sense considering Horizon is open world whilst Forza 4 is not).
Halo 4 is not way better than the top titles on consoles. I personally think it's about as good as the best (Killzone 3 and God of War 3).
Although it is the best looking game on the 360 by a pretty good amount.