My wife and I have been visiting this cosy little eatery for about 15 years now. They hit a bit of a rough patch around year 2000 when they changed ownership, and we did stop going for a few years, but we recently discovered their food is back to its former excellent form.
Whenever we visit Poseiden we order the Souvlaki. Nobody does it better. It's always very flavorful, and perfectly prepared. At some other restaurants I've been disappointed when the chicken Souvlaki just tastes like chicken. Not so at Poseiden, it's always strongly flavored with those distinctive and delicious Greek spices.
The Greek salad is also excellent. What makes Poseiden's Greek salad stand out is that it is never bitter like at some other Greek restaurants. I believe the difference is in the oil they use.
The rice is always perfect. Very moist, and very flavorful.
I would also say their tzatziki sauce is better than average. It's very tangy. I was very surprised to read the other review that claims the tzatziki is heavy on the garlic. I consulted my wife on this one and she agrees: it's just not true. The tzatziki is perfect.
The pita bread is average. No complaints, but nothing special. I usually ask them to withold the potato and vegetables as I just do not like them prepared the greek way.
Poseiden provides good value. The Souvlaki meal is $15 and includes everything I just mentioned, including 2 skewers of chicken or beef. For just two or three dollars more you can get the 3 skewer meal, which includes 1 each of chicken, beef, and lamb.