This is better:
2. My favorite class is math class.
This one is correct:
3. I have two math classes today.
Since you have TWO math classes, "classes" must be plural.
1. My favorite class is a math class.
2. My favorite class is math class.
(Which one is right? are both OK? Do they have a different meaning?)
3. I have two math classes today.
4. I have two math class today.
(Which one is right?)
2 answers
If you're taking two math classes, then it would be more accurate to say "My favorite class is algebra (or geometry or trigonometry)."