It really depends on a lot of factors, mate. I knew a guy in college who, when singing acapella, had a great voice. But put him with a band / backing track / even duetting with another singer, the guy was HIDEOUSLY tone-deaf.
Now, for hitting notes, here's something I got him to try, and it worked (to a point, I am no singing tutor, there was only so far I could help him): Listen to something that makes the same note for a long time, either stand at a keyboard and choose a long-sustaining sound, hit one key and keep it there. Start humming anywhere you like in terms of notes. Then slowly bend your note up or down until you hear it "match" the note you are playing. You can even do it when someone is vacuum cleaning in your house! A lot of appliances have a constant note. This is one way to practice hitting notes perfectly, in time when you hear a note, you'll be able to hit it bang-on first time.
Now on to the sound of your voice. This is more about what you are happy with. You can try to listen to other artists and try to emulate their voice. A REALLY easy one to emulate is Eddie Vedder, as he's got that certain "sound" to his vocal. Scott Stapp is another one who is easy to emulate, and his songs with Creed are easy to learn and sing for practice.
It's either emulation, or learn to be happy with your own voice. Listen to your fave songs, and try to sing them in YOUR voice. I know it's easy to automatically emulate the sound of a particular vocalist you are listening to, but try not to. When I started singing, I would emulate Mike Patton. This is about 17 years ago, when I first got into Faith No More. I always sang with that "American" accent that every singer, no matte what country they are from, tries to sing with. It's due to saturation, a lot of songs in the charts will have someone singing in an American accent, probably because that's where their influences come from.
About 10 years ago I kinda dissected this and thought "I am British, why do I sing like and American?" so I stopped doing it. It was hard to adjust, like trying to break in a new pair of hard leather boots, but in time I defined my own sound, and I sing in a British accent now. No, not like Lily-Allen and all the other wannabe-cockney clones, I have my own style, and I'm really happy with it. Sometimes, keeping it real is the best way to make yourself happy.
Try to clear all influences from your head and sing in YOUR voice, you might be pleasantly surprised!