Making one good video game is hard enough. Some studios and franchises attempt the impossible by making a cohesive trilogy of games with a connected story. Ongoing franchises are different because they are not always as dependent on each other, but trilogies have something special about them.
Unfortunately, all the trilogies mentioned below fumbled the ball during the conclusion. Not all of the third games here are bad, but they all have something that prevented the them from achieving true greatness. Even though the trilogy is not perfect, there are still two fantastic games to play prior to the third title.
10 F.E.A.R.
The original F.E.A.R. is a unique blend of intense first-person shooter action and spine-tingling horror. The enemy AI is notably intelligent, making for unique gunfights at every turn. The sequel continues this trend but with more varied environments. The third game went for a cooperative focus, removing the horror altogether. Though each player has distinct abilities, the level design and action feel flat. Co-op is awesome, but not when it sacrifices part of the series identity.
9 Dead Space
The first two Dead Space games are the most terrifying games of the generation. The Resident Evil 4 influence is apparent, but it manages to blend in some slower, old school scares at the same time. Dead Space 3 not only adds co-op, but there are also annoying microtransactions. The bigger focus on action disappointed most of its fanbase. There are rumors of a revival circulating, and hopefully it ignores all the changes Dead Space 3 brought to the table.
8 Ninja Gaiden
The Ninja Gaiden reboot from 2004 is still seen as one of the finest action games ever made. It is also difficult to the point of turning off many newcomers.
The sequel continues this trend, but the third game in the series was criticized for lacking the intricacy of the prior entries. This is perhaps due to it not being directed by Tomonobu Itagaki, who is also responsible for the Dead or Alive series.
7 Resident Evil 4 Through 6
Even though it is a long-running franchise, Resident Evil 4 through 6 kind of represents a trilogy all its own. This is when the series utilized the over-the-shoulder camera and a more action-oriented tone. Resident Evil 4 is a masterpiece and the fifth game adds co-op but still manages to maintain some tension. Resident Evil 6 just goes over the top and jumps the shark. Fortunately, the series returned to its roots with Resident Evil 7: Biohazard.
6 Doom
Doom and Doom 2 are similar in look and tone. It took 10 years to get Doom 3, which aimed for a slower, more horrific approach. Demons overwhelming your screen is replaced with methodically going through hallways and using your flashlight to see the environments. It is not necessarily a bad game, but it does not really feel like a proper successor. The reboot in 2016 manages to perfectly translate the classic gameplay to the medium.
5 Dino Crisis
Dino Crisis has been out of the spotlight for a long time. Fans would probably have a lot more entries to play if the Xbox exclusive Dino Crisis 3 didn't receive such jeers from both fans and critics upon release. Where the debut entry is a great Resident Evil clone and the sequel is a fun action game for the PS1, Dino Crisis 3 is set in space and barely resembles the prior two entries except for the use of dinosaurs.
4 Banjo Kazooie
It is hard to call Banjo Kazooie: Nuts & Bolts the conclusion of a trilogy. It came out so many years after Banjo Tooie and the gameplay is radically different from its predecessors. It is easy to definitively say that it was not what fans wanted from the series, especially after the long wait. The idea is sound and even fun, but fans were more interested in a straightforward 3D platformer. Perhaps Microsoft will bring it back one day in its true glory.
3 Mega Man Legends 3
Even though Mega Man Legends 3 never came out, it was announced and deserves mention because people actually got to play it. Capcom let fans play a beta version on the 3DS to receive feedback on the title. The fact people played it makes its cancellation all the more painful. Mega Man Legends 2 ends with the titular character getting stuck on the moon. Fans thought he'd finally come down, but he is still waiting to be freed from his Luna trap.
2 Parasite Eve
The first two Parasite Eve are unique for their setting and use of real-time mechanics, a rarity for the genre during the time. A third entry only came out on the PSP in 2010 called The 3rd Birthday.
Reviews were mostly mixed, and fans would have preferred a PS3 game instead. It is often considered the worst of the series. Few except fans recall this series, but many are still holding out hope for a revival or remake.
1 Mass Effect
Mass Effect is considered one of the best gaming trilogies of all time, even after the third game slipped and fell right at the endzone. Mass Effect 3 is still fantastic, but the ending left much to be desired. It ignores all the choices players made during the trilogy, instead of leaving it all up to one final decision. An update tried to remedy fans' grievances, but it did not fix everything. All the same, it is absolutely worth it to play through the trilogy.