One clear day landing a B737 from the south on 28L into KSFO we were cleared for a visual to 28L. A B747 was cleared for a visual on a head on course with us from the north to 28R. I noticed he was going to overshoot so simply leveled off, let him slide underneath us and waited til he got back on his runway centerline to descend and reintercept the 28L glideslope. We were side by side, same altitude and about 500 ft apart on the approach as per normal at SFO after he got established. We felt it was not an event worth writing up so that was the end of it. We were 500 ft apart on final with zero altitude difference and felt totally safe. This is normal procedure at SFO. This thing with SWA is getting silly.