If it were my house i would make a wood planked ramp..i dont know your budget but pavers,sand and paver base can be expensive for that size of area and will be a super pain to level and as said in an earlier post will not stay level for long. not too mention the slope of ur lawn will channel all rainwater down this hill and thus erode away sand and paver base over time making it a never ending project.Concrete will look very nice but also will be pretty expensive. with the wood ramp u can grade it to what ever steepness u would like and then u could use brick retaining walls on the sides to make a nice garden area on the sides maybe even a cascading waterfall down the side of the ramp,maybe even have a the waterfall go under a bridge type section of your walkway to the other side. And with the wood u can make it whatever color u would like. a nice deck ontop of the hill would be awsome as well just a suggestion hope it helps!keep us posted on what u decide to do!