Vector graphics just won't work for runtime applications like games ; the hardware works with textures and vertex/pixel/geometry processing units, that's about it, basically GPUs don't "understand" the shapes used to describe objects built in vector format, i.e. contours/splines/formulas.
Unless you want to ignore all hardware acceleration and create a custom vector-based engine, in which case performance is likely to become a problem, rasterisation is inevitable.
Nevertheless, there's no reason your resources should become excessively pixelated ; have you tried simply exporting at a higher resolution ? It costs a bit of memory and disk space, but the performance is still good.