S1: one of the best TV seasons ever produced.
S2: mostly just as good.
S4: Even worse... until the final third which is amazing.
S5: Alias: The Next Generation. Spin-off. Lame.
Unfortunately ALIAS will always be one of those missed opportunities to me, a show that started out brilliant and quickly faded into blandness. The first season promised such a fascinating in-depth storyline of secrets and answers that never surfaced. It basically started out as LOST and quickly became homogenized.