Babies need to be held and loved on. It is temporary. Soon your crying one will be an active little person who likes to play with his toys. Enjoy it while you can.
But if they crying seems to be persistant, take him to the doctor to make sure nothing is wrong.
Also there is nothing wrong with putting him in the swing or laying him on a mat and letting him cry for a bit. He needs you love but he also needs to learn at an early age that he can't cry all the time to get what he wants. At this age, I say more cuddling and less crying =)
You are a good mother. Don't feel guilty about not spending enough time with your 2 1/2 year old. Read to him, snuggle with him when you can. Otherwise, he can learn to play on his own while you are in the same room with him. When the babies are asleep, or at least the crying one is asleep, make sure to spend extra time with your 2 year old.
And make sure you get plenty of rest. If you need help, ask for it. Family and friends will lend a helping hand.
Good Luck =)