2. - because it was the first movie in the trilogy, with less characters and less of an overall plot and a much smaller budget...it was essentially an introduction to the x-men universe...you will notice that in X-men United that Singer introduced more characters, while having a more involved plot and the movie WAS over two hours... now in X-men last stand you have plot points from the previous movies to resolve, the story of Last Stand itself, about 6 more characters than the previous films to explore and the largest budget of the three and yet oddly the shortest running time of the three...