They're both stimulants. That's about it.
Ecstacy acts by releasing dopamine, seratonin and norepiniphrine
Nictoine acts by releasing a wide variety of chemicals including acetylcholine, norepinephrine, epinephrine, vasopressin, arginine, dopamine, autocrine agents, and beta-endorphin.
Ecstasy's effects are stimulating, euphoric and enantogenic
Nicotine's effects are purely stimulating at low doses and sedating and analgesic at high doses.
Ecstasy is non-addictive.
Nicotine isn't.
There's limited evidence that ecstasy has any negative long term health effects.
There's plenty of evidence of nicotine's long term negative health effects.
Ecstasy is a synthetic chemical
Nicotine is an natural product