I'm not always opposed to sequels, because a lot of linear games of the current generation are considerably shorter than games for, say, the PS1, and, also, games take a lot of time to create, so I give them the benefit of the doubt and just assume that it takes developers three games to cover the story they want to tell. Like Assassin's Creed or Mass Effect for example. Those games clearly came out with a pre-existing intention for the story to continue - they already knew where they wanted the story to go.
Where I don't like sequels and feel like they're just milking a cash cow is when they're continuing a story that's already ended - where there's no point in continuing a series because it's not adding anything to the experience; just a carbon copy of the original. Tomb Raider and LoZ are probably the most obvious choices, although Resident Evil & the new Silent Hill spin offs are up there, because they have almost no continuity or connection to what the original games were trying to accomplish. They're just generic action games with a popular franchise stapled onto the box, and they basically detract from the glory that were the genuinely brilliant games in the series.
