The important thing to keep in mind is as follows: jealousy is triggered by a third party. I'll say it again: jealous feelings are triggered by a third party.
Let's modify the example you gave by adding the following component: you are very much attracted to your friend's wife. If your friend finds out about it and sees you chatting up his wife, he would likely display a measure of jealous behavior.
On the other hand, let's keep your example as it is. You say your friend's wife is "a very cute lady." Fine. Of you it could be said, "You're a little envious!" In other words, you might want (deep in the recesses of your unconscious mind!) what is not yours to have. Envy, by the way, is called the "green-eyed monster." Another saying is, "The grass is always greener on the other side of the hill." But I digress.
True, there are three parties involved in both of the above scenarios, but what triggers jealous feelings is one party's right (within reason, of course) to protect the third party (i.e., his wife). Your friend does NOT want to share his wife with another person--even you, his good friend. This is normal.
Jealous feelings get out of hand, however, when a husband becomes so suspicious of his wife's behavior, that every time she talks to another man, her husband flies into a jealous rage. Clearly he is overreacting (if in fact his wife is simply talking with another male in the normal course of events). Maybe she's just asking a guy for the time!
Jealous feelings can become a cancer in a committed relationship, because a critical element in the foundation to a good marriage is trust. When trust evaporates, jealousy rears its ugly head.
Being envious can also be destructive, like a cancer. An envious person is never satisfied with what she has but is forever gazing enviously on the abilities, gifts, possessions, and good looks of others. Contentment eludes her.
Which has a more "positive" implication? Offhand, I'd say neither.
Nevertheless, it is perfectly acceptable in normal conversation for you to say to your friend in a friendly, non-threatening way, "Hey man, I'm really envious of your for marrying such a great gal! I hope I do as well as you did when the time comes for me to marry!"
I've noticed that people today use the terms envious and jealous almost interchangeably, which is OK, I guess. If they use the word jealous, however, usually they mean envious, and when they use envious they could mean jealous.
Is it worth correcting people when they mix the two words up? If you're the teacher and they're the students, then OK; otherwise, just pride yourself on knowing the difference between the words envious and jealous and keep this knowledge to yourself!