They (pediatricians, other baby experts) will tell you that a baby should be sleeping through the night at 6 months, which is about the same time you can begin transitioning to mushy foods like cereals, which will keep him or her fuller longer than milk. What they don't tell you is that 6 hours is considered "through the night" for infants up to 2 years, so if you're trying to put L.O. down at 8 PM you can expect to be woken up at 2 AM every so often for quite some time.
At 28 months, your child should be long used to genuinely sleeping through the night (8-10 hours) on his own. He seems to be stuck in the same sleep patterns a young infant has, sleeping hard for two to three hours, waking up from light Stage 1 or 2 sleep and not knowing how to fall back asleep on his own (because he never learned; he always fell asleep in Mommy's arms).
At first, I said Dr Ferber could kiss my first-time-parent ass; infants need to know that Mommy and Daddy are there when they're needed, or they don't learn how to trust, which can haunt them for life. However, there comes a time when love has to get a little tougher, and boundaries must be set. This typically starts about the year mark, or as soon as your baby's standing and cruising (and so can cause damage), whichever comes first. One of the boundaries is bedtime. He needs to learn that nighttime is Mommy and Daddy's time to sleep without him. If he needs them, they're there, but not at his every beck and call.
I still don't advise ignoring his cries outright. I advise going to him (or responding to him if he's old enough to get out of the crib or toddler bed and come to you), seeing if he's all right, and if there's no emergency like a dirty diaper or he's really hungry or thirsty, laying him back down in his crib (don't pick him up if he never left), tucking him in, and saying he needs to go back to sleep. He's not going to like this; it's not the reaction he's used to getting from you, which is to take him into the bedroom and let him fall asleep there. He'll wail; now you ignore it, at least for 15-30 minutes, before repeating the process. You're establishing a new cause-and-effect; crying or yelling for Mommy gets a response, but not the one he was after, and continuing to cry after Mommy's been in isn't doing anything for him except giving him a headache, sore throat and tiring him out.
Soon enough, he'll realize that there's nothing he can do while it's dark outside that will get him back into Mommy and Daddy's bed, and he'll adapt; he'll eventually learn to "self-soothe" when he wakes up, allowing him to fall back asleep after waking in a more adult sleep pattern, and for you to stay asleep.
Once this occurs, or as it's happening, you need to make sure you respond when your L.O. wakes up with more than a couple of perfunctory cries. My wife originally thought that our daughter, after the year mark, should be fine from sundown to sunup and that all crying was to be ignored. One night, after 45 minutes of persistent, "angry" crying, and against her sleepy command not to go, I went in to find her in soaked PJs, shivering and crying herself hoarse, because the cheap diapers we were trying couldn't handle overnight use (especially when bedtime was prefaced with a 10-ounce bottle). We resolved that night to differentiate between the sleepy "I'm awake, anyone gonna start my day?" crying and the "something is seriously wrong" crying (and to switch to better name-brand diapers for nighttime, and use up the cheap ones during the day).