This show went from "Great" to "Oh, come on!"
I recently finished the Alias marathon of all 5 seasons.
The first two seasons were great and I really enjoyed them. It was great to see all the dangers Sydney had to go through to bring down SD-6 and The Alliance. With the fall of The Alliance the show started to go downhill. It was lacking a clear enemy and direction. I understand the creators and writers wanted to move to a new direction and introduce new characters and plotlines, but with the exception of Melissa George (Lauren Reed in season 3), they were all uninteresting. Particularly Balthazar Getty (Thomas Grace in Season 5) and Rachel Nichols (Rachel Gibson in Season 5) were bland and forgettable. I know it was an attempt to introduce new characters instead of Sydney and Vaughn, but the choices were poor. But these are not the things that bothered me the most.
What drove me insane were the incredibly stupid decisions of characters and nonsensical and unexplained story arcs.
First of all, there were so many times that Sydney, Vaughn, Jack and others were betrayed by Sloane, Irina, Sark and others and they trust them again and again which leads to another betrayal. There were so many times when I yelled at the screen: "Shoot him/her. You've got a gun in your hand, use it. Just shoot him/her and a great deal of your problems will be over." But nooooooooo, why bother? Let's put some more trust into the person who will inevitably betray you again and maybe even try to kill you. Sloane, Sark, Irina, Katya, Elena Derevko, Lauren Reed, etc. Or at least have that person arrested and locked somewhere noone ever finds them again and throw away the key. No, why bother, right? Make sure you keep on visiting that person repeatedly until they find a way to get to you. I could go on like this all day.
The other thing was the impossibility of some events - most of all the shooting of Vaughn. I know the creators intended Sydney and Vaughn to have a happy ending and so it was obvious Vaughn would come back, but the shooting was simply impossible to survive. He took some 10 to 15 bullets to chest and his internal organs would have been shredded. No way he would have survived that. Plus many more instances of simply impossible to survive situations.
The last nuisance was the whole Rambaldi plot. I never really understood who he was. A great inventor - sure, why not. But there's no way in hell he would have known anything about genetics and mobile phones. How the heck did he come up with that Horizon? A levitating sphere granting eternal life? Hello? And other inventions? Like brain-wave scan in 15th century? How did he know what brain-waves are and how did he know the exact patters of Nadya? Sure, he's just a McGuffin and some suspension of disbelief is required, but this was stretching it.
Like I said, I enjoyed the show in the first and second season, the third one was ok, but the fourth and especially the fifth one diminished the previous viewing experience. I would still rate is a 6 out of 10. It is definitely worth checking out.