It can be tempting to interpret Psalm 37:4 as meaning if we want God to bless us, all we have to do is love Him. "Name it and claim it", as some say. If I want a flashy car, be good to God. Because apparently, God is in the practice of taking bribes...
In reality, delighting in God means delighting in God. God, of course, is a Heavenly being. Do you think He is especially concerned with the car you drive, the job you work, the school you attend, the hobbies you indulge in, or any other worldly affair? Do you really think it matters to God whether or not your team wins? And as long as your spouse is Godly, do you think He cares if the world would consider them beautiful? All of these things are worldly, and of course God is not of this world, neither does He call us to be.
So what does it really mean that if we delight in the Lord, He will give us the desires of our hearts? The focus point of the verse isn't "the desires of our hearts", but "delight in the Lord". When we delight in the Lord, our desires start to change. We stop worrying about the earthly things we want and instead start thinking about how we can use our worldly things to glorify Him.
Maybe God doesn't want you to be a world class CEO because you can reach a lost soul as a high school janitor? Maybe God doesn't want you to have a flashy sports car because you can help your struggling neighbor with a minivan? Maybe you didn't get into a specific college/university because another one will teach you something you can actually use later? And if you truly delight in God, you will start to want all of that!
As with any other place in the Bible, Psalm 37:4 should be read as if God is the focus. Prosperity preachers do the opposite: Man is the focus. In 2 Timothy 3:15-17, we read that the Scriptures were inspired by God for purposes of making us wise to salvation, for doctrine, for reproof, for correction, and for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work. Nowhere, not even once, does the Bible say that if there's something you really want, all you have to do is love God, and you'll get it.
In fact, the opposite is true. In James 4:3, James tells us "You ask and do not receive, because you ask amiss, that you may spend it on your pleasures." (Emphasis mine). When we use the Bible as if it was a genie's instruction manual, we aren't really delighting in the Lord. Christianity is a servant and master relationship, and it should be a no brainer which role belongs to God. Thus, if we really want God to give us the desires of our hearts, it is essential that the desires of our hearts become what God desires to give us. Anything else is as close to idolatry as you can get without directly blaspheming.