That is a gentle slope and actually, as others have said, looks appropriate for draining water away from the garage.
If you were to build it up on the low end at the fence, you would need a low wall to hold the soil. I would not do this for a couple of reasons:
[*]Water must drain somewhere. If you make the area level, it will have no where to go. I know you said it puddles there (and I don't quite understand why), but leveling it out will make the drainage worse. You are lucky that it is graded this way.[*]You are making a lot of work for yourself. Sometimes you have to analyze the best solution...one that is reasonable as far as time and costs go.
Here is what I would do.
[*]I would eliminate the grass completely by planting ground cover. This will be totally low maintenance.[*]It looks shady and if so, you could use Pachysandra, Vinca (slower grower) or Ivy (good if you live in the North U.S.).[*]Since you have the room, install bluestone stepping stones for access from the front to the back. You can level them and slightly re-grade at a steeper amount towards your neighbor. You really are not suppose to re-grade to create issues for neighbors, but I think this grade will still be pretty small. In addition, the plants will absorb water to help.
Now you have a pretty area, access, and no mowing. Here are some photos. These are much more involved than what I had in mind...the areas are wider and various plants were used (which you could do too if you wanted too) instead of a simple ground cover.
The time, money and effort you were going to spend leveling out the area could be spent creating something practical and lovely!
Thanks. This is a good idea and I might go with this, but u mentioned about the cost and really i have all the stuff i need to do my idea that's why i was going to do it. But now since i went here i realize that my idea probably wouldn't have solved anything. Thanks.