In my opinion, fresh veggies always taste better regardless of how they're prepared... but since you asked about frozen, here's an easy way to cook frozen peas:
In a sauce pan, saute a tablespoon of garlic in a tablespoon of butter over medium heat. Add a bag of frozen peas, a tsp of dried thyme and a pinch of salt and sugar with a couple of grinds of pepper. Put the lid on and allow the peas to steam for a few minutes until cooked.
You can do the same with frozen corn, just skip the pinch of sugar and consider adding a sprinkle of red chili flakes. If you're feeling really indulgent, you can add a little cream at the end and cook it down to make a "creamed" corn sauce.
Other than frozen corn and peas, I think veggies loose too much texture to taste OK from the freezer.
For fresh cooked veggies, my favorite are skillet green beans with lemon from the Cooks Illustrated side dish cookbook. In a tbs of olive oil, add 1 lb of fresh green beans (haricot verts, the skinny ones cook fastest, and are the most tender) and saute until they start to darken the skin a little (about 5 min), add another tablespoon of olive oil in the middle of the pan with a couple cloves of crushed garlic, a sprinkle of chili flake and a tsp of thyme, cook for just 30 seconds to a minute while sprinkling two heaping tablespoons of flour over the green beans (sorry, I don't measure much and don't follow the recipe to a T anymore, I've made it so many times).
Stir the garlic and spices into the green beans to mix in the flour and cook for another minute to mellow the flour. Add a cup of chicken stock the the pan, lower the heat, cover and cook until the beans are tender (about 5 min). Once the beans are cooked, the sauce will be thickened and delicious. Off the heat, stir in some fresh lemon juice to taste (I usually use half of lemon) and serve.
The complete recipe has you top them with a mix of toasted breadcrumbs and parmasen cheese, which is a nice touch but not always necessary. I make a big batch of crumbs and leave them in the fridge to use whenever needed. Saves some time.