EPS is a notoriously large format, and there’s no point using it for this because ListPlot3Ds can’t be exported as vector graphics anyways. Try a raster format like Export["G1.png", Graph1] or Export["G1.jpg", Graph1].
I do not think 66 Kb EPS can be considered as a large file, especially If we take into consideration that Mathematica’s EPS Export does not apply any compression which EPS format supports. As a comparison Exporting into PNG with good (but not excellent) resolution 300 dpi produces a file of size 136 Kb:
Export["pl.png", pl, ImageResolution -> 300]
In version 10 we face the fact that vector Exporting of 3D plots into PDF is disabled by default and even explicit setting of option AllowRasterization -> False does not work. I hope that it is a bug which will be fixed.
Now The problem arises is that, the size of exported file “G1.eps” is very high. Near about 10 MB.
In such situation the best what can be done is to rasterize only the plot itself, keeping axes and labels in vector form. This problem was investigated for the first time by StackOverfow participant jmlopez and me in the thread “Rasters in 3D graphics.” A solution for Mathematica 7 was developed. The proposed approach was further developed by Mathematica.SE participant halirutan in this answer. Note the huge number of upvotes: this functionality is highly appreciated by the community!