Is it worth partitioning a Table by single value in Oracle?
My opinion is that partitioning of that table in the manner presented may be useful.

Your queries will be two times faster (in the case when partitions are almost equal) if they make full scans. 

In case your queryes have another tone of filters/conditions and use indexes, partitioning is not useful, because the level of an index is almost not affected by doubling the number of values.

UPDATE: For the test you did (SELECT * FROM table1 WHERE TENANTID=2) it is sure that partitioning is best. The bitmap solution need to scan the index, and after this, to scan all table's blocks containing rows with tenantid=2(it knows what are the rows). But partitioning will cause just scanning the table's partition with tenantid=2. They are phisically separated to tenantid=1.

So, two scans(index scan + table scan) vs one table scan(wich may be smaller).