Does an electric fireplace really generate heat or are they just for show?

There are both kinds.   

Some are just for show and some have a "heating element" inside. Those put out a little heat, but not enough that you could use it as your only heat source in a cold house.

They're mostly for show but you can get them that have a heating element built in.  They won't provide any more heat than a conventional space heater, but it's still something.

you'll have to check on the individual fireplace--some are also heaters, some aren't. The one I have is also a small space heater, which only warms the immediate vicinity, but it's fine when I turn down the main heat in my house and sit in my living room. But a lot the ones I see don't have that ability. 

They are heaters made to look like organic burning fires like log or coal or gas  with generated  flames that are not real flames , but the heater element is below , there are decorative ones that are not heaters but decorative flames that are not real , so you ask for each individual purchase what it is or you want 

Both kinds exist
Some just for show
Others are heaters

If it has a heater built in they can make a room very comfortable plus romantic.

Some are just glorified fan heaters. They are just a feature.

They're for show. 

Am I the only person who has noticed the poster using '?' as a user name i answering every question with two or more answers; on this question i saw 3 of his answers.

They are for both.   

There is some heat given off, but mainly they are for show not warmth!

The cheapest ones are just for show. But I have 2 that also put out heat too ...meaning a glorified electric room heater.

depends on the model some do heat and others are show pieces .

There are both. My cousin has one that has heat in her living room. Her house runs colds and she says it does help keep the living room warmer. It is the room the hang out. 

The "heater" part of a fake fireplace is a glorified space heater. Most are rated for 1400 to 1600 watts max. Just like a regular space heater, the effectiveness is determined by the air space the heater has to heat. The smaller the room, the more effective the fireplace will be to heating that area. But if it is placed into a large living room like mine is, one can only feel a bit of heat coming from it, but it will never effectively heat the area. Sit close and enjoy, but snuggle up in a wrap or blanket to get really warm!

I believe so,.......

They will put out 3.4 btu's per watt/hour. So if is a model with just a 60 watt bulb, it won't put out much heat, less than 200 btu's per hour. If it has 1500 watt coil or infrared unit it will put out about 5120 btu's per hour.

No, the fire on an electric chimney isn't genuine.

The warmth is given from the warming component that is independent to the fire.  Since the fire isn't genuine, no unsafe gases or smoke is created from and electric chimney. This implies that electric chimneys can be utilized without the requirement for a smokestack, pipe or vent.

very little heat mainly just for show