On the whole, I think The Last Stand is what ruined and tainted Marsden's characterisation of Cyclops in the public consciousness tbh. He was served well enough by X1, I thought. Yeah, Logan and Rogue were the main focus, but Cyclops himself was clearly the leader of the team, was confident, and called the shots in the final showdown.
X2, though disappointing as far as the amount of Cyclops in it, is justifiable on account of the story it's trying to tell. If Singer had been able to come back for X3 after doing Superman Returns, like he'd wanted, I think Cyclops would have likely been a key component of the story, and the trilogy as a whole would have served Cyclops a lot better.
Unfortunately, Fox wanted to rush and so Singer couldn't take part in X3, and Marsden couldn't participate to the extent he wanted. Thus, Cyclops ends up feeling like an afterthought in those movies. The Last Stand was the make or break for his character.