Lessee...
Final Fantasy VII took down the Final Fantasy series. I like my heroes to have emotions and all, but I don't quite enjoy playing as whiny suicidal myanthropes. Top that all off with being puzzled why people continue to want to throw their lives into the hands of these people? IX was a somewhat refreshing look to the older Final Fantasys, but was a great 3 disc RPG, too bad it was 4 discs long (the last disc just... well... sucked.) VIII was the biggest offender to the overly unlikable hero. X, not sure, Tidus just reminded me too much of someone I didn't like in school, so, there wasn't much pathos. The Villians also came off as crap. Sephiroth is a whiny goth kid Mamma's boy who goes on temper tantrums. The Sorceress... well, hard to be fearful of someone with a speech impediment and is only introduced at the end of disc 3. As stated earlier with IX, the game should have ended earlier. Now, Final Fantasy Tactics Advance was interesting as Marche is, for all intensive purposes, the villian of FFTA. You go about destorying the crystals to end the world.
Genso Suikoden IV was a heavy slap in the face for old time Suikoden players. III had some issues to it, but IV just felt seven ways to wrong. The Combat was dumbed down to Final Fantasy levels, the characters were poorly modeled, and the character relationships were crap, again, dumbing it down to a Final Fantasy level. Thankfully Tactics and V sat down and reminded us why we started playing this series in the first place.
I'll agree that Halo 1 was a major disappointment. Cookie-cutter characters, not very diverse weapons (aside from "The human guns are decent, the alien guns suck" which is a major U-Turn to the usual opposite). Level designs that were non-existant (Corridor, Big room with a small glass room in the middle, corridor, bridge, corridor, big room with a small glass room in the middle, corridor, bridge...)
The Mana/Seiken Densetsu series after Legend of Mana. They try. Lord do they try, but they keep dropping the ball repeatedly forgetting why we loved Secret of Mana, SoM3, Legend, and Final Fantasy Adventure/Sword of Mana.
Command and Conquor Red Alert 2, for what some other people have noted about other C&C games, it forgot it's roots as a cold-war era RTS with the idea that both sides of the war had access to all the technologies we drooled over and wished we had, and in Red Alert 2, it felt more like everyone had C&C Tiberium Wars-era toys. (Side note, Renagade should have been awesome...)