If the tables are big in size, selecting count(*) will take long time. Better analyze all tables and then select num_rows from user_tables.

SQL>spool analyze.sql;
SQL> select 'analyze table '||table_name||' compute statistics;' from user_tables;
SQL>spool off;
SQL>@analyze.sql
SQL>select table_name, num_rows from user_tables;

Hope this helps.

Sanjay