I have a confession to make. I really like disaster movies. The Poseidon Adventure is clearly the best of the lot, but I also have a lot of love for the Airport series. I know they're terrible--seriously, the line between the Airport pictures and Airplane! and it's equally hilarious sequel is a fine line indeed. Still, there's something about those abusrdities that I cherish. Airport '75 is surely my favorite, yeah, Lancaster is a legend, but he's no Charlton Heston. Of course, this comes from a guy who loves The Omega Man, so take it for what's worth.
Oh, about The Omega Man--if you look at it as a strict adaptation of Matheson's novel I Am Legend, it's a total jive-turkey. If you look at it as something unique that was loosely based on Matheson's text, it's a hell of a good time and one of Heston's best. That's my take, anyway.