i may purchase Oblivion on PC if and only if I can spawn enemies with the console command such as rats,lions,bandits,etc. Thanks

You can but you must be careful. If you overuse the console command for spawning enemies, then your savegame may bloat and end up corrupted.

The command for spawning enemies / creatures is placeatme "ID of the spawned creature", just without the quotation marks. You can find IDs on the corresponding pages, for instance, IDs for lions are http://www.uesp.net/wiki/Oblivion:Rat#Mountain_Lions as are IDs for all animals.

ok thanks what about humaniods like bandits?

Could you elaborate on this? I've used the spawn commands in Skyrim... A lot. Yet never had my save bloat up. Is this Oblivion specific?

I read it on UESP and it says that it can be potentially dangerous, I don't have any experiences with it because I never use this command.

They are somewhere onhttp://vgstrategies.about.com/library/doswin/bl_Oblivion_PC_NPC_Codes.htm.