How about:

SELECT 'INSERT INTO Temp_Table (TableName, Count) SELECT '''||Owner||'.'||Table_Name||''', COUNT(*) FROM '||OWNER||'.'||TABLE_NAME||';'
FROM DBA_TABLES
WHERE OWNER NOT IN ('SYS', 'SYSTEM')
ORDER BY Table_Name

This would give you output like:

INSERT INTO Temp_Table (TableName, Count) SELECT 'OWNER1.TABLENAME1', COUNT(*) FROM OWNER1.TABLENAME1;
INSERT INTO Temp_Table (TableName, Count) SELECT 'OWNER2.TABLENAME2', COUNT(*) FROM OWNER2.TABLENAME2;
Just spool and run

cheers

Ben