ok that is a super obvious question, how about I ask a better one.
Marriage is a huge commitment. Do you trust your partner with your life? Will you grow sick of them, or will they grow sick of you?
Marriage is fun, but you need to look far into the future. You need to ask yourself why you value them right now.
Maybe they're attractive. Maybe they get along really well with your friends. But what if you find different friends? What if your partner's looks fade?
You need to look at the factors that you KNOW will still apply in 20 years.
Do they get along with your family? This is a big one, because we never find different parents/brothers/sisters.
Do you have similar dreams of the future? Do you have compatible careers?
These are the real questions to ask, as these are the things that don't always change.
For instance, if one of you wants to live in a penthouse suite while the other wants to live on an acreage in the middle of the mountains, it might be a good idea to think things through a bit. Finding middle ground isn't always an option if two people are radically different.
Hope I helped.