Genasi:
Genies, beings of elemental power, masters of the Elemental Planes, sometimes produce offspring with mortal races. From their mortal slaves or from powerful mortals among the planes whom the genies consider allies, friends, and rarely, equals; these children are mortal humanoids with elemental power flowing through their veins. Called genasi, these planetouched individuals are more common in planar sites such as Sigil and the City of Brass, but since the Godswar, many fled to the Prime as refugees and stayed there. On Antheron, they are more common in the south, in towns with a high content of planar refugees, such as Portal and Rhys-Zekhal. Genasi have little to no contact with the elemental masters who sired their bloodline, and most alive today are several generations removed from the elemental progenitors of their bloodline. They come in 4 varieties, one of each element, from each subtype of genie.

All Genasi have the following traits:
Ability Score Increase: Based on elemental subtype, see below.
Alignment: Genasi are just as varied as humans, but those with a closer connection to their planar values may take on one aspect of the alignment of their genie ancestor
Age: Genasi age at the same rate as humans, but live longer
Size: Genasi are about the same size as humans, their size is Medium
Speed: Base walking speed is 30 feet.
Type: Genasi are Humanoids with the (Elemental) subtype.
Darkvision: Genasi have superior vision in dark and dim conditions. They can see in dim light within 60 feet as if it were bright light, and in darkness as if it were dim light. Color cannot be discerned in these conditions, only black and white
Elemental Resistance: Every subtype has resistance to the energy type which corresponds to their elemental heritage.
Languages: Genasi speak Common and the dialect of Primordial that corresponds to their elemental heritage.

Air Genasi: Descended from the noble Djinn, air genasi have varying shades of blue skin and dark eyes. Their build is slight, and their hair is usually pale white, some shade of blue, or black, and always appears either windswept or as if it is flowing in a constant gentle breeze. Some view themselves as inheritors of the sky, the wind, and the very air of the world. They can be very cam and collected, but when driven to action, they are swift and decisive.
Ability Score Increase: Dexterity score increases by 2 and Intelligence increases by 1
Breathless: Air Genasi do breathe, but the elemental nature of their bodies generates air within their lungs. As such, they can hold their breath indefinietely.
Elemental Resistance: Air Genasi have resistance to electricity damage.
Elemental Legacy: Air Genasi can cast the Feather Fall spell once, they regain the ability to do so after a long or short rest. At 5th level, an Air Genasi can cast one more elemental spell per day. This spell must be either Levitate or Gust of Wind. The genasi can choose which spell to use at the time of casting, but only a long rest can restore the ability to cast either. Intelligence is their spellcasting ability for these spells.
Language: Air Genasi speak the Auran dialect of Primordial.

Earth Genasi: Descended from the malicious Dao, earth genasi have stocky builds and skin with a rocklike appearance, either pebbly or having the appearance of being chisled or cracked. Their skin tones range from pale gray to earthy brown and their eyes appear gemlike, with colors of green, amber, or black. Their hair is usually brown, although male earth genasi are frequently bald. They tend to be slow to act, seemingly ponderous in thought, but once they do decide to act, they become driven to accomplish what they set their minds to.
Ability Score Increase: Constitution increases by 2, Strength increases by 1.
Stability: Earth Genasi have a strong connection to the earth beneath their feet. Whie they have their feet on the ground, they have advantage on Strength saving throws to avoid any kind of forced movement.
Elemental Resistance: Earth Genasi have resistance to acid damage.
Elemental Legacy: Earth Genasi can cast the Thunderwave spell once as a 1st level spell, they regain the ability to do so after a long or short rest. At 5th level, they can cast one spell per day. This spell must be either Spike Growth or Melf's Acid Arrow as a 2nd level spell. The genasi can choose which spell to use at the time of casting, but only a long rest can restore the ability to cast either. Intelligence is their spellcasting ability for these spells.
Language: Earth Genasi speak the Terran dialect of Primordial.

Fire Genasi: Descended from the avaricious Efreet, Fire Genasi have the most variety in their builds, with some powerful with broad shoulders, and others wiry and sinuous. Their skin ranges from shades of red to black, often having a burnt appearance. Their hair waves like flames, and is usually red, blond, or white, and their eyes sometimes seem to burn when they are angry. They tend to be bright and creative, but also proud, and quick to action, if not anger. They can be very excitable, and their passions burn fiercely, but they are also sometimes seen as flighty.
Ability Score Increase: Intelligence increases by 2, Strength increases by 1
Control Flame: Fire Genasi can affect small nonmagical flames within 30 feet of themselves, causing them to flicker, brighten, dim, or change color. They can also instantaneously snuff out unattended nonmagical flames, such as candles, torches or campfires.
Elemental Resistance: Fire Genasi have resistance to fire damage.
Eemental Legacy: Fire Genasi know the Produce Flame cantrip. At 5th level, they may cast one spell per day, which must either be Flame Blade or Scorching Ray both as a 2nd level spell. The genasi can choose which spell to use at the time of casting, but only a long rest can restore the ability to cast either.
Language: Fire Genasi speak the Ignan dialect of Primordial.

Water Genasi: Descended from the enigmatic Marids, Water Genasi have thick-waisted builds, and run the gamut from stocky and muscular to ponderous and obese. Their skin appears in colors of light greens and blues, often appearing to be wet, clammy, or covered in fine fish scales. Their hair is similarly of green or blue hues, and their eyes are usually blue or black. They are just as comfortable in water as out. They tend to be easygoing and friendly, most often content to follow the path of least resistance, but when angered, they can be relentless and unyielding as the tides.
Ability Score Increase: Wisdom increases by 2, Constitution increases by 1
Aquatic: Water Genasi can breathe underwater and have a swim speed equal to their land speed (including any encumbrance from armor).
Elemental Resistance: Water Genasi have resistance to cold damage.
Elemental Legacy: Water Genasi can cast the spell Create or Destroy Water once as a 1st level spell, they regain the ability to do this after a long or short rest. At 5th level, they may, once per day, use the Swiftcurrent ability, which is a bonus action to activate, and allows the Water Genasi to assume a liquid-like state until the end of his turn. During that time, he ignores the movement impairment of difficult terrain, takes no damage from damaging terrain, provokes no attack of opportunity for his movement, and can move through enemy spaces without penalty. He still must end his movement in an empty space.
Language: Water Genasi speak the Aquan dialect of Primordial.


Alternative
I was also thinking, in an effort to make them al feel like subraces of the same race, of giving them all +1 STR
and breaking down racially as follows:
Air: +2 DEX
Earth: +2 CON
Fire: +2 INT
Water: +2 WIS

Thoughts? Comments and Criticism welcome. Haven't implemented this, it's still in Alpha, as it were.