R3 is a general kernel names, like 22D, 30F, 31H, 40B, 45B, 46C, 4.7 (R3E). It came out from R2 (2 Tires). R3 is 3 tires(DB/AP/frontend).
all MM/PP/SD/FI/CO modules will running on top of it.
ECC is new set of SAP package and it's running on new Netweaver kernel
ECC 5.0 = ERP2004 running Netweaver 2004
ECC 6.0 = ERP2005 running NetWeaver 2004s
Portal is part of Netweaver
Portal 6.0 is part of Netweaver 2004
Portal 7.0 is part of Netweaver 2004s(same as BI 7.0 )