Comparativos y superlativos
Javier Bardem es mayor que Jennifer Lopez. Jennifer Lopez es menor que Javier Bardem.(1) You can also use mayor in this case.
Note: Nearly all Spanish people incorrectly use mayor, bysaying *más mayor (*more bigger, *more older). If you hear Spanish people saying that, do not suppose that they are right and you are wrong. It's is right the way you did it =)
You did it almost a perfect. Just remember: After superlative we use de instead of en.
Comparativos y superlativos
Javier Bardem es mayor que Jennifer Lopez. Jennifer Lopez es menor que Javier Bardem.