I guess you are referring to algorithms "Hierarchical", "Organic", "Orthogonal", "Circular", "Tree", "Radial", "Series Parallel" from the "Layout" menu with "7 basic layouts". Well, these are indeed all the major algorithms available.
"Tools" -> "Create Graph" creates sample graphs for testing purposes. Thus it does not make sense to use "Create Graph" with yEd's Excel import (because the import will create the graph). Moreover, the sample graphs created with "Create Graph" are actually arranged with the layout algorithms available in the "Layout" menu - e.g. "Tools" -> "Create Graph" -> "Tree" uses the algorithm "Layout" -> "Tree" -> "Directed" with default settings.
If the layout of a graph imported from Excel does not look as nice as the layout of a sample graph created with "Tools" -> "Create Graph" -> "Tree", then this is probably due to the Excel graph having a different structure than the sample graph.
Are you sure that the graph imported from Excel is actually a tree? If your graph is not a tree, the algorithm will identify a tree structure in your graph, arrange that structure, and afterwards add in non-tree edges using a general purpose edge routing algorithm. The routing for these non-tree edges is usually very different from the routing for the tree edges and thus non-tree edges look bad most of the time. In such cases it is usually a good idea to use the hierarchical layout algorithm instead of the tree layout algorithm.
