In general, I've been giving nominations a lot of leeway for how they fit the category: three games in a row on the same platform, by the same publisher, continuing the same story arc, etc. But there are some that are hard to fit into those trilogy-paths, so I wanted to bring them up here.
GOOD EXAMPLES
- Resident Evil - the first three were tightly-packed PS1 releases - later games that continued the series came out on other systems
- Halo - even though there are more than three in the numbered series, the first three were Bungie-developed and concluded their narrative arc - later games picked up a different story
- Banjo-Kazooie/-Tooie/Nuts & Bolts - even though these games span console generations, there are only three in the "main" series, so it counts
- Devil May Cry - I assume this is the same kind of situation as Resident Evil above, where the PS2 trilogy can be considered on its own - leaning towards including
- Uncharted - While we could consider the PS3 entries under the precedent set above, the main difference is Uncharted 4 continues and concludes their narrative arc rather than reposition or resituate things. Because of that, I'm inclined to consider this a 4-game series rather than a proper trilogy - leaning towards removing
- Mega Man 1-3 (NES) - There are 6 NES Mega Man games and nothing to distinguish the first three as a discrete trilogy.
- Phoenix Wright: Ace Attorney (DS) - Someone needs to convince me that the trilogy formed by the first three games in the series stands apart from Apollo Justice and the 2 Phoenix Wright games after that. Is it because they all came out in 2001-4, Apollo Justice is a different main character, and the later Phoenix Wright games came out in 2013 on 3DS?
- Batman: Arkham - There are actually 4 games in this series (Asylum, City, Origins, Knight) that follow the same narrative arc and were all released within a close span of time on the same systems, so I can't think of any excuse to consider this a trilogy.
- Half-Life - As amazing as this nomination is, and as much as I want it to get public recognition and appreciation, I'd rather not give people the option of a gag vote in the polls.