I googled "Why I am a Catholic" and I was surprised at just how many results matched that search. I thought about posting those results (I still might later), but I decided to post my own reasons.
1. The Eucharist
I can understand why it would seem weird to some, but if Jesus says He wants us to eat His flesh and His blood then that's what we should do. When He says that He is the bread come down from Heaven it is, well... the Gospel truth. I wrote once before on the Eucharist imagery in Nativity Scenes. And just as moving as it is to think and realize that Christ was physically present before the world after Mary gave birth to Him, it is very moving to me to realize that He is still physically present every day in masses all around the world.
2. Apostolic Tradition
Our teachings have been zealously guarded and passed down from Jesus Christ himself. Nobody else can make that claim. I know that some claim that the Catholic Church fell to Satan and that only a small remnant remained faithful, but the problem there is that the theory runs contrary to the Gospel. Jesus told Peter that the gates of Hell would NEVER prevail against the Church. If that theory is true then apparently the personal guarantee of Jesus is null and void.
Personal interpretations can lead one astray and very often they are conflicting. It is clear that Christ taught the objective truth. Christian truth cannot be both one way and another. Either contraception is immoral or it is not (I believe of course that it is immoral). The Catholic Church has authority, again, from Christ to teach. No other Christain Church has a basis for such a claim. Guided by the Holy Spirit, the Catholic Church speaks authoritatively.
If nothing else its always interesting to wonder what it would be like to hold God as an infant. More importamtly its fascinating to contemplate her central role in the Incarnation. She has pointed the way to Christ for untold numbers of Christians. She is the perfect role model for any Christian. When she told that she was pregnant with the Christ child her response was "[B]e it done unto me according to thy word." She accepted God's will over her own. But my favorite line from Mary in the Gospels is at the wedding of Cana when she says "Do whatever He tells you." The Catholic Church recognizes the powerful impact she can have on living a Christian life.
5. The Saints
As Saint Paul tells us in the scriptures there is "a great cloud of witnesses" watching us. We know that the angels in heaven pray. Surely then the faithful departed also pray and certainly in the eternity that is spent in heaven some prayers are said for those of us still on Earth. The Catholic Church is one of only a few Christian Churches that realize the potential of the prayers of those before the Throne.