So in my opinion the vanilla trees in minecraft are ugly. Because of my distaste for the the vanilla trees, I have come up with a five step method to improving trees in minecraft. each of these steps can be changed to achieve different results. To create better trees you will require access to the '/tree' command and you will also need access to simple world edit commands such as '//replace'

STEP 1.
The first step to improving your trees in minecraft is to avoid small tress at all costs, these trees are non improvable. when creating trees i tend to stick to larger trees. The larger the better. To get large trees pull out a stick from your inventory and type the command '/tree bigtree' then right click on the block where you want the tree. This will create a big tree. However sometimes when creating a big tree you might end up with a small-ish tree this could either mean two things. the are which you are trying to create the tree is too small or you just had some bad luck. if the tree is too small simply type '//undo' and place the tree down again. keep doing this until you get a tree of the size you want. when creating multiple trees in one are place all the trees down first before moving onto step 2. this way you can save your self a lot of time.

STEP 2.
After you have placed down all your trees, you want to go and select an area which contains all the leaves of the trees. Rather than building nerd poles, simply fly to a position that contains all the leaves and type '//pos1' then fly to the second position and type '//pos2'. Imagine the selected area as a box which all the leaves of the tree must fit (if you are unfamiliar with world edit i suggest watching a quick video on youtube to broaden your understanding of the plugin / mod). Once you have created a selection type in the following command '//replace leaves leaves,leaves,leaves,leaves,leaves,0,0,0,0,0,0,0,0,0' this will replace random leaves with air creating the effect of decay (No trees in real life are a solid lump of leaves, you can usually see straight through them). To change the density of the tree simply remove a '0'. If this still isn't dense enough simply undo and remove another '0'. Repeat this until you get the density of your liking.

STEP 3.
Once you have the look of the tree nailed, you need to improve the overall texture of the tree. In the texture pack I use, all the leaves are similar, so i can get away with using multiple leave types. However, if this isn't the case in your texture pack, find all the leaves that are similar and use those instead. To change the texture of the tree keep the area you selected from before and type the command '//replace leaves leaves,leaves:1,leaves:2,leaves:3,leaves:4,leaves:5,leaves:6' replacing the leaves:(n) with the leaves of your choice. you can also change the percentage of each leave used by adding an extra leave:(n) of your choice you can keep doing this until you achieve the look you are after.

STEP 4.
This step replaces the log block with a log block that has the log texture on all six sides. If you like the look of the tree with the rings exposed you can skip this step. However, if you wish to remove these, all you need to do is replace them with the log block which is textured on all six sides. This can be done by entering the following command '//replace log 17:12'. you can also experiment with using different log types by increasing the ':12' value by 1. You could also try having several log textures in one tree by using the previous command for leaves and replacing the leaves values with the log values. to find the block ID's for each block look up a ID table. (this is the one i use: http://minecraft-ids.grahamedgecombe.com/)

STEP 5.
No two trees are the same in the wild, so do not copy and paste trees. Where ever you need a tree, follow these steps and all your tress will look unique due to the random nature of world edit.