You already have many answers to your question, and several of them say that "yes, love is the most important thing". But they redefine the word love to be all-inclusive of many other traits and emotions and characteristics - so that it becomes every possible positive part of a relationship. Personally, I would not define love in this way. So my answer to you is no, I do not believe that love is the most important thing in marriage.
I know of perfectly workable marriages that are not based in love, but in other priorities. However, they do have the two ingredients which I think are necessary for a successful marriage. And these are respect and friendship. Some people would include honesty and trust, but I believe those are covered by respect, automatically. No person who is respectful of another would lie or betray them, so ipso facto, a respectful relationship is an honest and trustworthy one.
Friendship allows for companionship and the mutual sharing of pleasurable experience. It also allows for growth in the relationship, and flexibility, because friends appreciate and desire the well-being of each other. Friends also are capable of understanding and withstanding change, which is inevitable as time passes. Some changes are easy, and others are not. Friendship has the potential to weather the storms, while love - as I define it (not the all-encompassing, godlike version) - does not always manage to do this.